diff --git a/lib/jkqtcommon/jkqtpgeometrytools.cpp b/lib/jkqtcommon/jkqtpgeometrytools.cpp
index a0e7c43fdd..8f178e5296 100644
--- a/lib/jkqtcommon/jkqtpgeometrytools.cpp
+++ b/lib/jkqtcommon/jkqtpgeometrytools.cpp
@@ -103,9 +103,7 @@ QVector<QPolygonF> JKQTPUnifyLinesToPolygons(const QVector<QLineF> &lines, doubl
     }
     //return res.toVector();
     // clean the resulting polygon
-    for (QPolygonF& p: res) {
-        p=JKQTPCleanPolygon(p, distanceThreshold);
-    }
+    std::transform(res.begin(), res.end(), res.begin(), std::bind(&JKQTPCleanPolygon, std::placeholders::_1, distanceThreshold));
 
     int maxIterations=100;
     int iter=0;
@@ -266,7 +264,7 @@ QVector<QPointF> JKQTPAdaptiveFunctionGraphEvaluator::evaluate(double tmin, doub
     for (double t=tmin+delta_t0; t<tmax; t=t+delta_t0) {
         const double treal=t;
         intData.insert_after(a, std::pair<double, QPointF>(treal, fxy(treal)));
-        InternalList::iterator b=a; b++;
+        InternalList::iterator b=a; ++b;
         //qDebug()<<"t="<<t<<", dist(a,b)="<<std::distance(a,b);
         refine(intData, a, b, 0);
         //qDebug()<<"       after refine: dist(a,b)="<<std::distance(a,b);
@@ -299,7 +297,7 @@ void JKQTPAdaptiveFunctionGraphEvaluator::refine(JKQTPAdaptiveFunctionGraphEvalu
     const double slope_mid_b=(pb.y()-pmid.y())/(pb.x()-pmid.x());
     if (fabs(slope_mid_b-slope_a_mid)>slopeTolerance || delta>minPixelPerSample) {
         intData.insert_after(a, std::pair<double, QPointF>(tmid, pmid));
-        InternalList::iterator abmid=a; abmid++;
+        InternalList::iterator abmid=a; ++abmid;
         refine(intData, a, abmid, degree+1);
         refine(intData, abmid, b, degree+1);
     }
@@ -324,9 +322,7 @@ QVector<QPointF> JKQTPSplitPolylineIntoPoints(const QVector<QPointF> &line, std:
         for (int i=1; i<line.size(); i++) {
             const QVector<QPointF> ps=JKQTPSplitLineIntoPoints(QLineF(line[i-1], line[i]), fTransform);
             result.reserve(result.size()+ps.size());
-            for (auto& p: ps) {
-                if (result.size()==0 || result.last()!=p) result.push_back(p);
-            }
+            std::copy_if(ps.begin(), ps.end(), std::back_inserter(result), [&](const QPointF&p) { return result.size()==0 || result.last()!=p; });
             //qDebug()<<"line: "<<QLineF(line[i-1], line[i])<<"  --> ps.size()="<<ps.size()<<", result.size()="<<result.size();
         }
     }
diff --git a/lib/jkqtfastplotter/jkqtfastplotter.h b/lib/jkqtfastplotter/jkqtfastplotter.h
index 8a2c7cca28..2684095168 100644
--- a/lib/jkqtfastplotter/jkqtfastplotter.h
+++ b/lib/jkqtfastplotter/jkqtfastplotter.h
@@ -397,7 +397,7 @@ class JKQTFASTPLOTTER_LIB_EXPORT JKQTFastPlotter : public QGLWidget {
         /** \brief return x-pixel coordinate from x coordinate */
         inline double x2p(double x) {
             if (xAxisLog) {
-                if (x<0) return xOffset+log(xMin/10.0)/JKQTPSTATISTICS_LN10*xScale;
+                if (x<=0) return xOffset+log(xMin/10.0)/JKQTPSTATISTICS_LN10*xScale;
                 return xOffset+log(x)/JKQTPSTATISTICS_LN10*xScale;
             } else {
                 return xOffset+x*xScale;
@@ -416,7 +416,7 @@ class JKQTFASTPLOTTER_LIB_EXPORT JKQTFastPlotter : public QGLWidget {
         /** \brief return y-pixel coordinate from y coordinate */
         inline double y2p(double y) {
             if (yAxisLog) {
-                if (y<0) return yOffset-log(yMin/10.0)/JKQTPSTATISTICS_LN10*yScale;
+                if (y<=0) return yOffset-log(yMin/10.0)/JKQTPSTATISTICS_LN10*yScale;
                 return yOffset-log(y)/JKQTPSTATISTICS_LN10*yScale;
             } else {
                 return yOffset-y*yScale;
diff --git a/lib/jkqtplotter/graphs/jkqtpbarchart.cpp b/lib/jkqtplotter/graphs/jkqtpbarchart.cpp
index 8cd6bcf73e..5a5c1813dd 100644
--- a/lib/jkqtplotter/graphs/jkqtpbarchart.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpbarchart.cpp
@@ -342,13 +342,13 @@ void JKQTPBarHorizontalGraph::draw(JKQTPEnhancedPainter& painter) {
     if (parent->getXAxis()->isLogAxis()) x0=transformX(parent->getXAxis()->getMin());
 //    double y0=transformY(0);
 //    if (parent->getYAxis()->isLogAxis()) y0=transformY(parent->getYAxis()->getMin());
-    double delta=1;
-    double deltap=0;
-    double deltam=0;
     {
         painter.save(); auto __finalpaint=JKQTPFinally([&painter]() {painter.restore();});
         intSortData();
         const bool hasStackPar=hasStackParent();
+        double delta=1;
+        double deltap=0;
+        double deltam=0;
         for (int iii=imin; iii<imax; iii++) {
             int i=qBound(imin, getDataIndex(iii), imax);
             double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i));
@@ -625,8 +625,8 @@ bool JKQTPBarHorizontalErrorGraph::getXMinMax(double &minx, double &maxx, double
                 if (start || xv<minx) minx=xv;
                 xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
-                if (start || xvv>maxx) maxx=xvv;
-                if (start || xvv<minx) minx=xvv;
+                if (xvv>maxx) maxx=xvv;
+                if (xvv<minx) minx=xvv;
                 xvsgz=xvv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
             }
diff --git a/lib/jkqtplotter/graphs/jkqtpcontour.cpp b/lib/jkqtplotter/graphs/jkqtpcontour.cpp
index b1f4346c2c..9e458033a2 100644
--- a/lib/jkqtplotter/graphs/jkqtpcontour.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpcontour.cpp
@@ -119,13 +119,13 @@ void JKQTPContourPlot::draw(JKQTPEnhancedPainter &painter)
             // transform into plot coordinates
             for(auto polygon =contourLinesCache.at(i).begin(); polygon!=contourLinesCache.at(i).end();++polygon ) {
                 contourLinesTransformedSingleLevel.push_back(QPolygonF());
-                for (auto& p: *polygon) {
-                    contourLinesTransformedSingleLevel.last().append(transform(x+p.x()/double(Nx-1)*width, y+p.y()/double(Ny-1)*height));
+                for (auto& poly: *polygon) {
+                    contourLinesTransformedSingleLevel.last().append(transform(x+poly.x()/double(Nx-1)*width, y+poly.y()/double(Ny-1)*height));
                 }
                 //qDebug()<<lineTranformed;
             }
-            for (const QPolygonF& p: contourLinesTransformedSingleLevel) {
-                painter.drawPolyline(p);
+            for (const QPolygonF& poly: contourLinesTransformedSingleLevel) {
+                painter.drawPolyline(poly);
             }
         }
     }
diff --git a/lib/jkqtplotter/graphs/jkqtpevaluatedfunction.cpp b/lib/jkqtplotter/graphs/jkqtpevaluatedfunction.cpp
index e676f6f8e0..d8a75f10df 100644
--- a/lib/jkqtplotter/graphs/jkqtpevaluatedfunction.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpevaluatedfunction.cpp
@@ -93,7 +93,7 @@ void JKQTPEvaluatedFunctionWithErrorsGraphDrawingBase::drawKeyMarker(JKQTPEnhanc
     if (drawLine) painter.setPen(p);
     painter.setBrush(b);
     if (fillCurve) painter.drawRect(rect);
-    if (!fillCurve & drawLine) painter.drawLine(QLineF(rect.left(), y, rect.right(), y));
+    if (!fillCurve && drawLine) painter.drawLine(QLineF(rect.left(), y, rect.right(), y));
 
 }
 
diff --git a/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.cpp b/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.cpp
index 536902eb0b..2d02bea262 100644
--- a/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.cpp
@@ -33,21 +33,33 @@
 
 
 
-JKQTPXYFunctionLineGraphBase::JKQTPXYFunctionLineGraphBase(JKQTBasePlotter* parent):
+JKQTPXYFunctionLineGraphBase::JKQTPXYFunctionLineGraphBase(double tmin_, double tmax_, JKQTBasePlotter *parent):
     JKQTPEvaluatedFunctionGraphBase(parent),
-    tmin(0.0),
-    tmax(1.0)
+    tmin(tmin_),
+    tmax(tmax_)
 {
     initLineStyle(parent, parentPlotStyle);
     setMaxRefinementDegree(8);
 }
 
+JKQTPXYFunctionLineGraphBase::JKQTPXYFunctionLineGraphBase(double tmin_, double tmax_, JKQTPlotter *parent):
+    JKQTPXYFunctionLineGraphBase(tmin_,tmax_,parent->getPlotter())
+{
+
+}
+
+JKQTPXYFunctionLineGraphBase::JKQTPXYFunctionLineGraphBase(JKQTBasePlotter* parent):
+    JKQTPXYFunctionLineGraphBase(0,1,parent)
+{
+}
+
 JKQTPXYFunctionLineGraphBase::JKQTPXYFunctionLineGraphBase(JKQTPlotter* parent):
     JKQTPXYFunctionLineGraphBase(parent->getPlotter())
 {
 
 }
 
+
 JKQTPXYFunctionLineGraphBase::~JKQTPXYFunctionLineGraphBase()
 {
 
@@ -161,13 +173,9 @@ JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(JKQTPlotter* parent):
 }
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(const jkqtpSimpleParametricCurveFunctionType &f, const QString &title_, double tmin_, double tmax_, JKQTBasePlotter *parent):
-    JKQTPXYFunctionLineGraph(parent)
+    JKQTPXYFunctionLineGraphBase(tmin_, tmax_, parent), plotFunction(), simplePlotFunction(f)
 {
-    tmin=tmin_;
-    tmax=tmax_;
     setTitle(title_);
-    plotFunction=jkqtpParametricCurveFunctionType();
-    simplePlotFunction=f;
 }
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(const jkqtpSimpleParametricCurveFunctionType &f, const QString &title_, double tmin_, double tmax_, JKQTPlotter *parent):
@@ -178,14 +186,9 @@ JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(const jkqtpSimpleParametricCu
 
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(jkqtpSimpleParametricCurveFunctionType &&f, const QString &title_, double tmin_, double tmax_, JKQTBasePlotter *parent):
-    JKQTPXYFunctionLineGraph(parent)
+    JKQTPXYFunctionLineGraphBase(tmin_, tmax_, parent), plotFunction(), simplePlotFunction(std::move(f))
 {
-    tmin=tmin_;
-    tmax=tmax_;
     setTitle(title_);
-    plotFunction=jkqtpParametricCurveFunctionType();
-    simplePlotFunction=std::move(f);
-    data.clear();
 }
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(jkqtpSimpleParametricCurveFunctionType &&f, const QString &title_, double tmin_, double tmax_, JKQTPlotter *parent):
@@ -195,14 +198,9 @@ JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(jkqtpSimpleParametricCurveFun
 }
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(jkqtpParametricCurveFunctionType &&f, const QString &title_, double tmin_, double tmax_, JKQTBasePlotter *parent):
-    JKQTPXYFunctionLineGraph(parent)
+    JKQTPXYFunctionLineGraphBase(tmin_, tmax_, parent), plotFunction(std::move(f)), simplePlotFunction()
 {
-    tmin=tmin_;
-    tmax=tmax_;
     setTitle(title_);
-    simplePlotFunction=jkqtpSimpleParametricCurveFunctionType();
-    plotFunction=std::move(f);
-    data.clear();
 }
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(jkqtpParametricCurveFunctionType &&f, const QString &title_, double tmin_, double tmax_, JKQTPlotter *parent):
@@ -212,14 +210,9 @@ JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(jkqtpParametricCurveFunctionT
 }
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(const jkqtpParametricCurveFunctionType &f, const QString &title_, double tmin_, double tmax_, JKQTBasePlotter *parent):
-    JKQTPXYFunctionLineGraph(parent)
+    JKQTPXYFunctionLineGraphBase(tmin_, tmax_, parent), plotFunction(f), simplePlotFunction()
 {
-    tmin=tmin_;
-    tmax=tmax_;
     setTitle(title_);
-    simplePlotFunction=jkqtpSimpleParametricCurveFunctionType();
-    plotFunction=std::move(f);
-    data.clear();
 }
 
 JKQTPXYFunctionLineGraph::JKQTPXYFunctionLineGraph(const jkqtpParametricCurveFunctionType &f, const QString &title_, double tmin_, double tmax_, JKQTPlotter *parent):
diff --git a/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.h b/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.h
index 3d25926907..989b123a72 100644
--- a/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.h
+++ b/lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.h
@@ -61,6 +61,13 @@ public:
     /** \brief class constructor */
     JKQTPXYFunctionLineGraphBase(JKQTPlotter* parent);
 
+
+    /** \brief class constructor */
+    JKQTPXYFunctionLineGraphBase(double tmin_, double tmax_, JKQTBasePlotter* parent);
+
+    /** \brief class constructor */
+    JKQTPXYFunctionLineGraphBase(double tmin_, double tmax_, JKQTPlotter* parent);
+
     /** \brief class destructor */
     virtual ~JKQTPXYFunctionLineGraphBase() override;
 
diff --git a/lib/jkqtplotter/graphs/jkqtpimagergb.cpp b/lib/jkqtplotter/graphs/jkqtpimagergb.cpp
index db41ac8592..36d285906a 100644
--- a/lib/jkqtplotter/graphs/jkqtpimagergb.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpimagergb.cpp
@@ -190,22 +190,22 @@ void JKQTPRGBMathImage::getOutsideSize(JKQTPEnhancedPainter& painter, int& leftS
         getDataMinMax(internalDataMin, internalDataMax);
         if (data) {
             if (colorBarRightVisible) {
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
+                if (!colorbarsSideBySide || !firstC) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
                 colorBarRightAxis->setRange(internalDataMin, internalDataMax);
                 colorBarRightAxis->setAxisWidth(sizeFactor*colorBarRelativeHeight*parent->getPlotHeight());
                 colorBarRightAxisB->setAxisLabel(imageNameR);
                 QSizeF s2=colorBarRightAxis->getSize2(painter);
                 QSizeF s1=colorBarRightAxis->getSize1(painter);
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.width()+s1.width());
+                if (!colorbarsSideBySide || !firstC) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.width()+s1.width());
             }
             if (colorBarTopVisible) {
-                //if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
+                //if (!colorbarsSideBySide || !firstC) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
                 colorBarTopAxis->setRange(internalDataMin, internalDataMax);
                 colorBarTopAxis->setAxisWidth(sizeFactor*colorBarRelativeHeight*parent->getPlotWidth());
                 colorBarTopAxisB->setAxisLabel(imageNameR);
                 QSizeF s2=colorBarTopAxisB->getSize2(painter);
                 QSizeF s1=colorBarTopAxisB->getSize2(painter);
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.height()+s1.height());
+                if (!colorbarsSideBySide || !firstC) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.height()+s1.height());
             }
             firstC=true;
         }
@@ -213,22 +213,22 @@ void JKQTPRGBMathImage::getOutsideSize(JKQTPEnhancedPainter& painter, int& leftS
         getDataMinMaxG(internalDataMinG, internalDataMaxG);
         if (dataG) {
             if (colorBarRightVisible) {
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
+                if (!colorbarsSideBySide || !firstC) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
                 colorBarRightAxisG->setRange(internalDataMinG, internalDataMaxG);
                 colorBarRightAxisG->setAxisWidth(sizeFactor*colorBarRelativeHeight*parent->getPlotHeight());
                 colorBarRightAxisB->setAxisLabel(imageNameG);
                 QSizeF s2=colorBarRightAxis->getSize2(painter);
                 QSizeF s1=colorBarRightAxis->getSize1(painter);
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.width()+s1.width());
+                if (!colorbarsSideBySide || !firstC) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.width()+s1.width());
             }
             if (colorBarTopVisible) {
-                //if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
+                //if (!colorbarsSideBySide || !firstC) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
                 colorBarTopAxisG->setRange(internalDataMinG, internalDataMaxG);
                 colorBarTopAxisG->setAxisWidth(sizeFactor*colorBarRelativeHeight*parent->getPlotWidth());
                 colorBarTopAxisB->setAxisLabel(imageNameG);
                 QSizeF s2=colorBarTopAxisB->getSize2(painter);
                 QSizeF s1=colorBarTopAxisB->getSize1(painter);
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.height()+s1.height());
+                if (!colorbarsSideBySide || !firstC) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.height()+s1.height());
              }
             firstC=true;
         }
@@ -236,22 +236,22 @@ void JKQTPRGBMathImage::getOutsideSize(JKQTPEnhancedPainter& painter, int& leftS
         getDataMinMaxB(internalDataMinB, internalDataMaxB);
         if (dataB) {
             if (colorBarRightVisible) {
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
+                if (!colorbarsSideBySide || !firstC) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
                 colorBarRightAxisB->setRange(internalDataMinB, internalDataMaxB);
                 colorBarRightAxisB->setAxisWidth(sizeFactor*colorBarRelativeHeight*parent->getPlotHeight());
                 colorBarRightAxisB->setAxisLabel(imageNameB);
                 QSizeF s2=colorBarRightAxis->getSize2(painter);
                 QSizeF s1=colorBarRightAxis->getSize1(painter);
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.width()+s1.width());
+                if (!colorbarsSideBySide || !firstC) rightSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.width()+s1.width());
             }
             if (colorBarTopVisible) {
-                //if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
+                //if (!colorbarsSideBySide || !firstC) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset);
                 colorBarTopAxisB->setRange(internalDataMinB, internalDataMaxB);
                 colorBarTopAxisB->setAxisWidth(sizeFactor*colorBarRelativeHeight*parent->getPlotWidth());
                 colorBarTopAxisB->setAxisLabel(imageNameB);
                 QSizeF s2=colorBarTopAxisB->getSize2(painter);
                 QSizeF s1=colorBarTopAxisB->getSize1(painter);
-                if (!colorbarsSideBySide || (colorbarsSideBySide && !firstC)) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.height()+s1.height());
+                if (!colorbarsSideBySide || !firstC) topSpace+=parent->pt2px(painter, colorBarWidth+colorBarOffset)+static_cast<double>(s2.height()+s1.height());
             }
             firstC=true;
         }
diff --git a/lib/jkqtplotter/graphs/jkqtpscatter.cpp b/lib/jkqtplotter/graphs/jkqtpscatter.cpp
index c9f3eec694..d0c5ce8579 100644
--- a/lib/jkqtplotter/graphs/jkqtpscatter.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpscatter.cpp
@@ -89,11 +89,6 @@ void JKQTPXYLineGraph::draw(JKQTPEnhancedPainter& painter) {
         if (imin<0) imin=0;
         if (imax<0) imax=0;
 
-        //qDebug()<<"JKQTPXYLineGraph::draw(): "<<3<<" imin="<<imin<<" imax="<<imax;
-        //double xold=-1;
-        //double yold=-1;
-        //bool first=false;
-        //QVector<QLineF> lines;
         std::vector<QPolygonF> vec_linesP;
         vec_linesP.push_back(QPolygonF());
         intSortData();
@@ -223,17 +218,18 @@ bool JKQTPXYLineErrorGraph::getXMinMax(double &minx, double &maxx, double &small
         if (imax<0) imax=0;
 
         for (int i=imin; i<imax; i++) {
-            double xvsgz;
             double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))+getXErrorU(i, datastore);
             if (JKQTPIsOKFloat(xv)) {
                 if (start || xv>maxx) maxx=xv;
                 if (start || xv<minx) minx=xv;
-                xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
-                xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))-getXErrorL(i, datastore);
+            }
+            xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))-getXErrorL(i, datastore);
+            if (JKQTPIsOKFloat(xv)) {
                 if (start || xv>maxx) maxx=xv;
                 if (start || xv<minx) minx=xv;
-                xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
             }
         }
@@ -269,13 +265,14 @@ bool JKQTPXYLineErrorGraph::getYMinMax(double &miny, double &maxy, double &small
             if (JKQTPIsOKFloat(yv)) {
                 if (start || yv>maxy) maxy=yv;
                 if (start || yv<miny) miny=yv;
-                double xvsgz;
-                xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
-                yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))-getYErrorL(i, datastore);
+            }
+            yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))-getYErrorL(i, datastore);
+            if (JKQTPIsOKFloat(yv)) {
                 if (start || yv>maxy) maxy=yv;
                 if (start || yv<miny) miny=yv;
-                xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
             }
         }
@@ -378,20 +375,21 @@ void JKQTPXYParametrizedScatterGraph::draw(JKQTPEnhancedPainter &painter)
     if (imin<0) imin=0;
     if (imax<0) imax=0;
 
-    //qDebug()<<"JKQTPXYLineGraph::draw(): "<<3<<" imin="<<imin<<" imax="<<imax;
-    double xold=-1;
-    double yold=-1;
-    bool first=false;
     QVector<QLineF> lines;
     QPolygonF linesP;
     QVector<QColor> linecols;
     QVector<QColor> linecolss;
     QVector<double> linewidths;
-    intSortData();
-    double specSymbSize=0;
-    bool hasSpecSymbSize=false;
+    //qDebug()<<"JKQTPXYLineGraph::draw(): "<<3<<" imin="<<imin<<" imax="<<imax;
     {
         painter.save(); auto __finalpaintinner=JKQTPFinally([&painter]() {painter.restore();});
+        double xold=-1;
+        double yold=-1;
+        bool first=false;
+
+        intSortData();
+        double specSymbSize=0;
+        bool hasSpecSymbSize=false;
         for (int iii=imin; iii<imax; iii++) {
             int i=qBound(imin, getDataIndex(iii), imax);
             double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i));
@@ -912,17 +910,18 @@ bool JKQTPXYParametrizedErrorScatterGraph::getXMinMax(double &minx, double &maxx
         if (imax<0) imax=0;
 
         for (int i=imin; i<imax; i++) {
-            double xvsgz;
-            double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))+getXErrorU(i, datastore);
-            double xvv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))-getXErrorL(i, datastore);
-            if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(xvv) ) {
+            const double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))+getXErrorU(i, datastore);
+            if (JKQTPIsOKFloat(xv)  ) {
                 if (start || xv>maxx) maxx=xv;
                 if (start || xv<minx) minx=xv;
-                xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
+            }
+            const double xvv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))-getXErrorL(i, datastore);
+            if (JKQTPIsOKFloat(xvv)) {
                 start=false;
                 if (start || xvv>maxx) maxx=xvv;
                 if (start || xvv<minx) minx=xvv;
-                xvsgz=xvv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=xvv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
             }
         }
@@ -955,17 +954,18 @@ bool JKQTPXYParametrizedErrorScatterGraph::getYMinMax(double &miny, double &maxy
         if (imax<0) imax=0;
 
         for (int i=imin; i<imax; i++) {
-            double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))+getYErrorU(i, datastore);
-            double yvv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))-getYErrorL(i, datastore);
-            if (JKQTPIsOKFloat(yv) && JKQTPIsOKFloat(yvv) ) {
+            const double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))+getYErrorU(i, datastore);
+            if (JKQTPIsOKFloat(yv)) {
                 if (start || yv>maxy) maxy=yv;
                 if (start || yv<miny) miny=yv;
-                double xvsgz;
-                xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
+            }
+            const double yvv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))-getYErrorL(i, datastore);
+            if (JKQTPIsOKFloat(yvv) ) {
                 if (start || yvv>maxy) maxy=yvv;
                 if (start || yvv<miny) miny=yvv;
-                xvsgz=yvv; SmallestGreaterZeroCompare_xvsgz();
+                const double xvsgz=yvv; SmallestGreaterZeroCompare_xvsgz();
                 start=false;
             }
         }
diff --git a/lib/jkqtplotter/graphs/jkqtpscatter.h b/lib/jkqtplotter/graphs/jkqtpscatter.h
index 93f25bd808..13d8ca91c0 100644
--- a/lib/jkqtplotter/graphs/jkqtpscatter.h
+++ b/lib/jkqtplotter/graphs/jkqtpscatter.h
@@ -57,7 +57,7 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPXYLineGraph: public JKQTPXYGraph, public JKQTP
         Q_OBJECT
     public:
         /** \brief class constructor */
-        JKQTPXYLineGraph(JKQTBasePlotter* parent=nullptr);
+        explicit JKQTPXYLineGraph(JKQTBasePlotter* parent=nullptr);
         /** \brief class constructor */
         JKQTPXYLineGraph(JKQTPlotter* parent);
 
diff --git a/lib/jkqtplotter/graphs/jkqtpspecialline.cpp b/lib/jkqtplotter/graphs/jkqtpspecialline.cpp
index 916f2b96ce..2c9402a5e5 100644
--- a/lib/jkqtplotter/graphs/jkqtpspecialline.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpspecialline.cpp
@@ -68,7 +68,7 @@ void JKQTPSpecialLineHorizontalGraph::drawKeyMarker(JKQTPEnhancedPainter& painte
     if (m_drawLine) painter.setPen(p);
     painter.setBrush(b);
     if (m_fillCurve) painter.drawRect(rect);
-    if (!m_fillCurve & m_drawLine) painter.drawLine(QLineF(rect.left(), y, rect.right(), y));
+    if (!m_fillCurve && m_drawLine) painter.drawLine(QLineF(rect.left(), y, rect.right(), y));
     if (m_drawSymbols) {
         plotStyledSymbol(parent, painter, rect.center().x(), rect.center().y(), rect.width()*0.5);
     }
@@ -308,8 +308,8 @@ void JKQTPSpecialLineHorizontalGraph::draw(JKQTPEnhancedPainter& painter) {
     if (m_drawSymbols) {
         painter.save();
         auto __finalpaintsym=JKQTPFinally([&painter]() {painter.restore();});
-        for (auto& p: ps) {
-            plotStyledSymbol(parent, painter, p.x(), p.y());
+        for (auto& ppoint: ps) {
+            plotStyledSymbol(parent, painter, ppoint.x(), ppoint.y());
         }
     }
 
@@ -480,9 +480,9 @@ void JKQTPSpecialLineVerticalGraph::draw(JKQTPEnhancedPainter& painter) {
 
     if (m_drawSymbols) {
         painter.save();
-        auto __finalpaint=JKQTPFinally([&painter]() {painter.restore();});
-        for (auto& p: ps) {
-            plotStyledSymbol(parent, painter, p.x(), p.y());
+        auto __finalpaintsym=JKQTPFinally([&painter]() {painter.restore();});
+        for (auto& point: ps) {
+            plotStyledSymbol(parent, painter, point.x(), point.y());
         }
     }
 
diff --git a/lib/jkqtplotter/graphs/jkqtpstatisticsadaptors.cpp b/lib/jkqtplotter/graphs/jkqtpstatisticsadaptors.cpp
index 1d9e3ba43d..6fa08c85c1 100644
--- a/lib/jkqtplotter/graphs/jkqtpstatisticsadaptors.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpstatisticsadaptors.cpp
@@ -35,9 +35,11 @@ JKQTPXFunctionLineGraph *jkqtpstatAddLinearWeightedRegression(JKQTPXYGraph *data
     JKQTBasePlotter* plt=datagraph->getParent();
     JKQTPDatastore* ds=plt->getDatastore();
     JKQTPYGraphErrorData* ge=dynamic_cast<JKQTPYGraphErrorData*>(datagraph);
-
-    JKQTPASSERT_M(ge!=nullptr, "datagraph needs to be convertible to JKQTPYGraphErrorData with a dynamic_cast!");
-    return jkqtpstatAddLinearWeightedRegression(plt, ds->begin(datagraph->getXColumn()), ds->end(datagraph->getXColumn()), ds->begin(datagraph->getYColumn()), ds->end(datagraph->getYColumn()), ds->begin(ge->getYErrorColumn()), ds->end(ge->getYErrorColumn()), coeffA, coeffB, fixA, fixB, &jkqtp_inversePropSaveDefault<double>);
+    if (ge) {
+        return jkqtpstatAddLinearWeightedRegression(plt, ds->begin(datagraph->getXColumn()), ds->end(datagraph->getXColumn()), ds->begin(datagraph->getYColumn()), ds->end(datagraph->getYColumn()), ds->begin(ge->getYErrorColumn()), ds->end(ge->getYErrorColumn()), coeffA, coeffB, fixA, fixB, &jkqtp_inversePropSaveDefault<double>);
+    } else {
+        throw std::runtime_error("datagraph needs to be convertible to JKQTPYGraphErrorData with a dynamic_cast!");
+    }
 }
 
 JKQTPXFunctionLineGraph *jkqtpstatAddRobustIRLSLinearRegression(JKQTPXYGraph *datagraph, double *coeffA, double *coeffB, bool fixA, bool fixB, double p, int iterations)
@@ -60,8 +62,11 @@ JKQTPXFunctionLineGraph *jkqtpstatAddWeightedRegression(JKQTPXYGraph *datagraph,
     JKQTPDatastore* ds=plt->getDatastore();
     JKQTPYGraphErrorData* ge=dynamic_cast<JKQTPYGraphErrorData*>(datagraph);
 
-    JKQTPASSERT_M(ge!=nullptr, "datagraph needs to be convertible to JKQTPYGraphErrorData with a dynamic_cast!");
-    return jkqtpstatAddWeightedRegression(plt, type, ds->begin(datagraph->getXColumn()), ds->end(datagraph->getXColumn()), ds->begin(datagraph->getYColumn()), ds->end(datagraph->getYColumn()), ds->begin(ge->getYErrorColumn()), ds->end(ge->getYErrorColumn()), coeffA, coeffB, fixA, fixB, &jkqtp_inversePropSaveDefault<double>);
+    if (ge) {
+        return jkqtpstatAddWeightedRegression(plt, type, ds->begin(datagraph->getXColumn()), ds->end(datagraph->getXColumn()), ds->begin(datagraph->getYColumn()), ds->end(datagraph->getYColumn()), ds->begin(ge->getYErrorColumn()), ds->end(ge->getYErrorColumn()), coeffA, coeffB, fixA, fixB, &jkqtp_inversePropSaveDefault<double>);
+    } else {
+        throw std::runtime_error("datagraph needs to be convertible to JKQTPYGraphErrorData with a dynamic_cast!");
+    }
 }
 
 JKQTPXFunctionLineGraph *jkqtpstatAddRobustIRLSRegression(JKQTPXYGraph *datagraph, JKQTPStatRegressionModelType type, double *coeffA, double *coeffB, bool fixA, bool fixB, double p, int iterations)
diff --git a/lib/jkqtplotter/jkqtpbaseplotter.cpp b/lib/jkqtplotter/jkqtpbaseplotter.cpp
index d8a0f0a738..2845e310b2 100644
--- a/lib/jkqtplotter/jkqtpbaseplotter.cpp
+++ b/lib/jkqtplotter/jkqtpbaseplotter.cpp
@@ -239,11 +239,6 @@ JKQTBasePlotter::JKQTBasePlotter(bool datastore_internal, QObject* parent, JKQTP
     actSavePDF=new QAction(QIcon(":/JKQTPlotter/jkqtp_savepdf.png"), tr("Save P&DF"), this);
     actSavePDF->setToolTip(tr("Save as PDF"));
     //toolbar->addAction(actSavePDF);
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-    actSavePS=new QAction(QIcon(":/JKQTPlotter/jkqtp_saveps.png"), "Save P&S", this);
-    actSavePS->setToolTip("Save as PostScript");
-    //toolbar->addAction(actSavePS);
-#endif
     actSaveSVG=new QAction(QIcon(":/JKQTPlotter/jkqtp_savesvg.png"), tr("Save S&VG"), this);
     actSaveSVG->setToolTip(tr("Save as Scalable Vector Graphics (SVG)"));
     //toolbar->addAction(actSaveSVG);
@@ -278,9 +273,6 @@ JKQTBasePlotter::JKQTBasePlotter(bool datastore_internal, QObject* parent, JKQTP
     connect(actShowPlotData,   SIGNAL(triggered()), this, SLOT(showPlotData()));
 
     connect(actSavePDF,    SIGNAL(triggered()), this, SLOT(saveAsPDF()));
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-    connect(actSavePS,     SIGNAL(triggered()), this, SLOT(saveAsPS()));
-#endif
     connect(actSaveSVG,    SIGNAL(triggered()), this, SLOT(saveAsSVG()));
     connect(actSavePix,    SIGNAL(triggered()), this, SLOT(saveAsPixelImage()));
 
@@ -700,9 +692,15 @@ void JKQTBasePlotter::setXY(double xminn, double xmaxx, double yminn, double yma
     xAxis->setRange(xminn, xmaxx);
     yAxis->setRange(yminn, ymaxx);
     if (maintainAxisAspectRatio) {
-        double mid=(yAxis->getMax()+yAxis->getMin())/2.0;
-        double w=fabs(xmaxx-xminn)/axisAspectRatio;
-        yAxis->setRange(mid-w/2.0, mid+w/2.0);
+        if (xAxis->isLinearAxis() && yAxis->isLinearAxis()) {
+            const double mid=(yAxis->getMax()+yAxis->getMin())/2.0;
+            const double w=fabs(xmaxx-xminn)/axisAspectRatio;
+            yAxis->setRange(mid-w/2.0, mid+w/2.0);
+        } else if (xAxis->isLogAxis() && yAxis->isLogAxis()) {
+            const double mid=(log(yAxis->getMax())+log(yAxis->getMin()))/2.0;
+            const double w=fabs(log(xmaxx)-log(xminn))/axisAspectRatio;
+            yAxis->setRange(exp(mid-w/2.0), exp(mid+w/2.0));
+        }
     }
     if (emitSignals) emit zoomChangedLocally(xAxis->getMin(), xAxis->getMax(), yAxis->getMin(), yAxis->getMax(), this);
 }
@@ -710,19 +708,31 @@ void JKQTBasePlotter::setXY(double xminn, double xmaxx, double yminn, double yma
 void JKQTBasePlotter::setX(double xminn, double xmaxx){
     xAxis->setRange(xminn, xmaxx);
     if (maintainAxisAspectRatio) {
-        double mid=(yAxis->getMax()+yAxis->getMin())/2.0;
-        double w=fabs(xmaxx-xminn)/axisAspectRatio;
-        yAxis->setRange(mid-w/2.0, mid+w/2.0);
+        if (xAxis->isLinearAxis() && yAxis->isLinearAxis()) {
+            const double mid=(yAxis->getMax()+yAxis->getMin())/2.0;
+            const double w=fabs(xmaxx-xminn)/axisAspectRatio;
+            yAxis->setRange(mid-w/2.0, mid+w/2.0);
+        } else if (xAxis->isLogAxis() && yAxis->isLogAxis()) {
+            const double mid=(log(yAxis->getMax())+log(yAxis->getMin()))/2.0;
+            const double w=fabs(log(xmaxx)-log(xminn))/axisAspectRatio;
+            yAxis->setRange(exp(mid-w/2.0), exp(mid+w/2.0));
+        }
     }
     if (emitSignals) emit zoomChangedLocally(xAxis->getMin(), xAxis->getMax(), yAxis->getMin(), yAxis->getMax(), this);
 }
 
-void JKQTBasePlotter::setY(double yminn, double ymaxx){
+void JKQTBasePlotter::setY(double yminn, double ymaxx) {
     yAxis->setRange(yminn, ymaxx);
     if (maintainAxisAspectRatio) {
-        double mid=(xAxis->getMax()+xAxis->getMin())/2.0;
-        double w=fabs(ymaxx-yminn)*axisAspectRatio;
-        xAxis->setRange(mid-w/2.0, mid+w/2.0);
+        if (xAxis->isLinearAxis() && yAxis->isLinearAxis()) {
+            const double mid=(xAxis->getMax()+xAxis->getMin())/2.0;
+            const double w=fabs(ymaxx-yminn)*axisAspectRatio;
+            xAxis->setRange(mid-w/2.0, mid+w/2.0);
+        } else if (xAxis->isLogAxis() && yAxis->isLogAxis()) {
+            const double mid=(log(xAxis->getMax())+log(xAxis->getMin()))/2.0;
+            const double w=fabs(log(ymaxx)-log(yminn))/axisAspectRatio;
+            xAxis->setRange(exp(mid-w/2.0), exp(mid+w/2.0));
+        }
     }
     if (emitSignals) emit zoomChangedLocally(xAxis->getMin(), xAxis->getMax(), yAxis->getMin(), yAxis->getMax(), this);
 }
@@ -1438,14 +1448,14 @@ void JKQTBasePlotter::gridPaint(JKQTPEnhancedPainter& painter, QSizeF pageRect,
             for (int i=0; i< gridPrintingList.size(); i++) {
                 //std::cout<<"printing "<<i<<" ...\n";
                 painter.save(); auto __finalpaintinnerloop=JKQTPFinally([&painter]() {painter.restore();});
-                int t_x=0;
-                int t_y=0;
+                int gt_x=0;
+                int gt_y=0;
                 //std::cout<<"printing "<<i<<" @g "<<gridPrintingList[i].x<<", "<<gridPrintingList[i].y<<" ...\n";
                 //std::cout<<"colrowlistsizes     "<<gridPrintingColumns.size()<<", "<<gridPrintingRows.size()<<" ...\n";
-                for (size_t j=0; j<gridPrintingList[i].x; j++) {  t_x+= static_cast<int>(gridPrintingColumns[static_cast<int>(j)]);  }
-                for (size_t j=0; j<gridPrintingList[i].y; j++) {  t_y+= static_cast<int>(gridPrintingRows[static_cast<int>(j)]); }
+                for (size_t j=0; j<gridPrintingList[i].x; j++) {  gt_x+= static_cast<int>(gridPrintingColumns[static_cast<int>(j)]);  }
+                for (size_t j=0; j<gridPrintingList[i].y; j++) {  gt_y+= static_cast<int>(gridPrintingRows[static_cast<int>(j)]); }
                 //std::cout<<"printing "<<i<<" @ "<<t_x<<", "<<t_y<<" ...\n";
-                painter.translate(t_x, t_y);
+                painter.translate(gt_x, gt_y);
                 gridPrintingList[i].plotter->drawPlot(painter, showOverlays);
 
             }
@@ -1505,14 +1515,14 @@ void JKQTBasePlotter::gridPaintOverlays(JKQTPEnhancedPainter &painter, QSizeF pa
             for (int i=0; i< gridPrintingList.size(); i++) {
                 //std::cout<<"printing "<<i<<" ...\n";
                 painter.save(); auto __finalpaintinnerloop=JKQTPFinally([&painter]() {painter.restore();});
-                int t_x=0;
-                int t_y=0;
+                int gt_x=0;
+                int gt_y=0;
                 //std::cout<<"printing "<<i<<" @g "<<gridPrintingList[i].x<<", "<<gridPrintingList[i].y<<" ...\n";
                 //std::cout<<"colrowlistsizes     "<<gridPrintingColumns.size()<<", "<<gridPrintingRows.size()<<" ...\n";
-                for (size_t j=0; j<gridPrintingList[i].x; j++) {  t_x+= static_cast<int>(gridPrintingColumns[static_cast<int>(j)]);  }
-                for (size_t j=0; j<gridPrintingList[i].y; j++) {  t_y+= static_cast<int>(gridPrintingRows[static_cast<int>(j)]); }
+                for (size_t j=0; j<gridPrintingList[i].x; j++) {  gt_x+= static_cast<int>(gridPrintingColumns[static_cast<int>(j)]);  }
+                for (size_t j=0; j<gridPrintingList[i].y; j++) {  gt_y+= static_cast<int>(gridPrintingRows[static_cast<int>(j)]); }
                 //std::cout<<"printing "<<i<<" @ "<<t_x<<", "<<t_y<<" ...\n";
-                painter.translate(t_x, t_y);
+                painter.translate(gt_x, gt_y);
                 gridPrintingList[i].plotter->drawOverlaysWithHints(painter);
 
             }
@@ -1752,10 +1762,10 @@ bool JKQTBasePlotter::printpreviewNew(QPaintDevice* paintDevice, bool setAbsolut
     bool res=false;
     if (printer) {
         if (!displayPreview || dlg->exec()==QDialog::Accepted) {
-            qDebug()<<svg<<printer<<delPrinter;
+            //qDebug()<<svg<<printer<<delPrinter;
             if (svg) {
                 printpreviewPaintRequestedNew(svg);
-            } else if (printer && !delPrinter) {
+            } else if (!delPrinter) {
                 printpreviewPaintRequestedNew(printer);
             } else {
                 printpreviewPaintRequestedNew(paintDevice);
@@ -2377,7 +2387,7 @@ void JKQTBasePlotter::drawNonGrid(JKQTPEnhancedPainter& painter, const QRect& re
         if ((scale*static_cast<double>(widgetWidth)/paintMagnification>static_cast<double>(rect.width())) || (scale*static_cast<double>(widgetHeight)/paintMagnification>static_cast<double>(rect.height()))) {
             scale=static_cast<double>(rect.height())/static_cast<double>(widgetHeight)*paintMagnification;
         }
-        painter.save(); auto __finalpaint=JKQTPFinally([&painter]() {painter.restore();});
+        painter.save(); auto __finalpaintinner=JKQTPFinally([&painter]() {painter.restore();});
         // scale the plot so it fits on the page
         painter.scale(scale, scale);
     #ifdef JKQTBP_DEBUGTIMING
@@ -3293,12 +3303,6 @@ QAction *JKQTBasePlotter::getActionSavePDF() const {
     return this->actSavePDF;
 }
 
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-QAction *JKQTBasePlotter::getActionSavePS() const {
-    return this->actSavePS;
-}
-#endif
-
 QAction *JKQTBasePlotter::getActionSavePix() const {
     return this->actSavePix;
 }
@@ -3704,51 +3708,12 @@ void JKQTBasePlotter::saveAsPDF(const QString& filename, bool displayPreview) {
     saveUserSettings();
 }
 
-void JKQTBasePlotter::saveAsPS(const QString& filename, bool displayPreview) {
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-    loadUserSettings();
-    QString fn=filename;
-    if (fn.isEmpty()) {
-        fn = QFileDialog::getSaveFileName(nullptr, tr("Save Plot"),
-                                    currentSaveDirectory,
-                                    tr("PostScript File (*.ps)"));
-        if (!fn.isEmpty()) currentSaveDirectory=QFileInfo(fn).absolutePath();
-    }
-
-    if (!fn.isEmpty()) {
-        QPrinter* printer=new QPrinter;
-        bool doLandscape=widgetWidth>widgetHeight;
-        if (gridPrinting) {
-            gridPrintingCalc();
-            doLandscape=gridPrintingSize.width()>gridPrintingSize.height();
-        }
-        if (doLandscape) {
-            printer->setOrientation(QPrinter::Landscape);
-        } else {
-            printer->setOrientation(QPrinter::Portrait);
-        }
-        printer->setOutputFormat(QPrinter::PostScriptFormat);
-        printer->setColorMode(QPrinter::Color);
-        printer->setOutputFileName(fn);
-        printer->setPageMargins(0,0,0,0,QPrinter::Millimeter);
-        printpreviewNew(printer, true, -1.0, -1.0, displayPreview);
-        delete printer;
-    }
-    saveUserSettings();
-#else
-    saveAsPDF(filename+".pdf", displayPreview);
-#endif
-}
-
 
 void JKQTBasePlotter::saveImage(const QString& filename, bool displayPreview) {
     loadUserSettings();
     QString fn=filename;
     QStringList filt;
     filt<<tr("Portable Document Format PDF [Qt] (*.pdf)");
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-    filt<<tr("PostScript [Qt] (*.ps)");
-#endif
     filt<<tr("Scalable Vector Graphics [Qt] (*.svg)");
     filt<<tr("PNG Image [Qt] (*.png)");
     filt<<tr("BMP Image [Qt] (*.bmp)");
@@ -3763,8 +3728,6 @@ void JKQTBasePlotter::saveImage(const QString& filename, bool displayPreview) {
     for (int i=0; i<writerformats.size(); i++) {
         filt<<QString("%1 Image (*.%2)").arg(QString(writerformats[i]).toUpper()).arg(QString(writerformats[i].toLower()));
     }
-    /*filt<<tr("X11 Bitmap [Qt] (*.xbm)");
-    filt<<tr("X11 Pixmap [Qt] (*.xpm)");*/
     QString selFormat="";
     if (fn.isEmpty()) {
         selFormat=currentFileFormat;
@@ -3795,14 +3758,9 @@ void JKQTBasePlotter::saveImage(const QString& filename, bool displayPreview) {
             }
         }
         //qDebug()<<"filtID="<<filtID<<"   isWithSpecialDeviceAdapter="<<isWithSpecialDeviceAdapter<<"   adapterID="<<adapterID;
-        int ids=0;
-        if (filtID==ids++) {
+        if (filtID==0) {
             saveAsPDF(fn, displayPreview);
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-        } else if (filtID==ids++) {
-            saveAsPS(fn, displayPreview);
-#endif
-        } else if (filtID==ids++) {
+        } else if (filtID==1) {
             saveAsSVG(fn, displayPreview);
         } else if (isWithSpecialDeviceAdapter && adapterID>=0 && adapterID<jkqtpPaintDeviceAdapters.size()) {
             QString tempFM="";
@@ -4222,9 +4180,7 @@ void JKQTBasePlotter::drawGraphs(JKQTPEnhancedPainter& painter){
 
 
     for (int j=0; j<graphs.size(); j++) {
-        //int leftSpace, rightSpace, topSpace, bottomSpace;
         JKQTPPlotElement* g=graphs[j];
-        //qDebug()<<"  drawing JKQTPPlotElement"<<j<<g->getTitle()<<g->metaObject()->className();
         if (g->isVisible()) g->draw(painter);
     }
 
@@ -4233,9 +4189,9 @@ void JKQTBasePlotter::drawGraphs(JKQTPEnhancedPainter& painter){
     }
 
     for (int j=0; j<graphs.size(); j++) {
-        int leftSpace, rightSpace, topSpace, bottomSpace;
         JKQTPPlotElement* g=graphs[j];
         if (g->isVisible()) {
+            int leftSpace, rightSpace, topSpace, bottomSpace;
             g->getOutsideSize(painter, leftSpace, rightSpace, topSpace, bottomSpace);
             ibTop+=topSpace;
             ibLeft+=leftSpace;
@@ -4518,10 +4474,10 @@ void JKQTBasePlotter::getKeyExtent(JKQTPEnhancedPainter& painter, double* width,
         double keyHeight=graphs.size();
         double w=0;
         double txtH=0;
-        QFont f=painter.font();
-        f.setFamily(plotterStyle.defaultFontName);
-        f.setPointSizeF(plotterStyle.keyStyle.fontSize*fontSizeMultiplier);
-        painter.setFont(f);
+        QFont floc=painter.font();
+        floc.setFamily(plotterStyle.defaultFontName);
+        floc.setPointSizeF(plotterStyle.keyStyle.fontSize*fontSizeMultiplier);
+        painter.setFont(floc);
 
 
         for (int i=0; i<graphs.size(); i++) {
@@ -4662,11 +4618,11 @@ void JKQTBasePlotter::getGraphsYMinMax(double& miny, double& maxy, double& small
 
 void JKQTBasePlotter::zoomToFit(bool zoomX, bool zoomY, bool includeX0, bool includeY0, double scaleX, double scaleY) {
    // std::cout<<"JKQTBasePlotter::zoomToFit():\n";
-    double xxmin=0;
-    double xxmax=0;
-    double xsmallestGreaterZero=0;
     if (graphs.size()<=0) return;
     if (zoomX) {
+        double xxmin=0;
+        double xxmax=0;
+        double xsmallestGreaterZero=0;
         getGraphsXMinMax(xxmin, xxmax, xsmallestGreaterZero);
         //std::cout<<"   xxmin="<<xxmin<<"   xxmax="<<xxmax<<std::endl;
         if (JKQTPIsOKFloat(xxmin) && JKQTPIsOKFloat(xxmax)) {
@@ -4708,11 +4664,11 @@ void JKQTBasePlotter::zoomToFit(bool zoomX, bool zoomY, bool includeX0, bool inc
             }
         }
     }
-    double yymin=0;
-    double yymax=0;
-    double ysmallestGreaterZero=0;
 
     if (zoomY) {
+        double yymin=0;
+        double yymax=0;
+        double ysmallestGreaterZero=0;
         getGraphsYMinMax(yymin, yymax, ysmallestGreaterZero);
         //std::cout<<"   yymin="<<yymin<<"   yymax="<<yymax<<std::endl;
         bool doScale=true;
diff --git a/lib/jkqtplotter/jkqtpbaseplotter.h b/lib/jkqtplotter/jkqtpbaseplotter.h
index 2f9be8c2bc..87b6d01cb2 100644
--- a/lib/jkqtplotter/jkqtpbaseplotter.h
+++ b/lib/jkqtplotter/jkqtpbaseplotter.h
@@ -208,7 +208,6 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPPaintDeviceAdapter {
  *   - print() prints the graph on a QPrinter object
  *   - saveAsPixelImage() saves the plot into a pixel image file (PNG, TIFF, ... formats, as supported by Qt)
  *   - saveAsPDF() saves the graph as a PDF file (using the Qt printing engine)
- *   - saveAsPS() saves the graph as a PDF file (using the Qt printing engine)
  *   - saveAsSVG() saves the graph as a SVG file (using the Qt SVG library)
  *   - saveImage() saves the graph
  * .
@@ -841,11 +840,7 @@ class JKQTPLOTTER_LIB_EXPORT JKQTBasePlotter: public QObject {
         QAction* getActionCopyMatlab() const;
         /*! \copydoc actSavePDF */ 
         QAction* getActionSavePDF() const;
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-        /*! \copydoc actSavePS */
-        QAction* getActionSavePS() const;
-#endif
-        /*! \copydoc actSavePix */ 
+        /*! \copydoc actSavePix */
         QAction* getActionSavePix() const;
         /*! \copydoc actSaveSVG */ 
         QAction* getActionSaveSVG() const;
@@ -1354,9 +1349,6 @@ class JKQTPLOTTER_LIB_EXPORT JKQTBasePlotter: public QObject {
         /** \brief save the current plot as a PDF file, with the current widget aspect ratio, if filename is empty a file selection dialog is displayed  */
         void saveAsPDF(const QString& filename=QString(""), bool displayPreview=true);
 
-        /** \brief save the current plot as a PS file, with the current widget aspect ratio, if filename is empty a file selection dialog is displayed */
-        void saveAsPS(const QString& filename=QString(""), bool displayPreview=true);
-
         /** \brief save the current plot as an image file, with the current widget aspect ratio, if filename is empty a file selection dialog is displayed.
         *          The image format is extracted from the file extension (jpeg, tiff, png, pdf, ...) */
         void saveImage(const QString& filename=QString(""), bool displayPreview=true);
@@ -2019,9 +2011,23 @@ class JKQTPLOTTER_LIB_EXPORT JKQTBasePlotter: public QObject {
         /** \brief the aspect ratio of plotwidth and plotheight to maintain, if \c maintainAspectRatio==true */
         double aspectRatio;
 
-        /** \brief indicates whether the axes should maintain an aspect ratio */
+        /** \brief indicates whether the axes should maintain an aspect ratio
+         *
+         *  \note An axis aspect ration is only well defined for linear axes (if both axes are linear).
+         *        If both axes a logarithmic, the axis ration is defined for log(axismax)-log(axismin).
+         *        For other combinations of axes, this function is deactivated
+         *
+         *  \see axisAspectRatio
+         */
         bool maintainAxisAspectRatio;
-        /** \brief the aspect ratio of axis widths to maintain, if \c maintainAxisAspectRatio==true */
+        /** \brief the aspect ratio of axis widths to maintain, if \c maintainAxisAspectRatio==true
+         *
+         *  \note An axis aspect ration is only well defined for linear axes (if both axes are linear).
+         *        If both axes a logarithmic, the axis ration is defined for log(axismax)-log(axismin).
+         *        For other combinations of axes, this function is deactivated
+         *
+         *  \see maintainAxisAspectRatio
+         */
         double axisAspectRatio;
 
 
@@ -2082,10 +2088,6 @@ class JKQTPLOTTER_LIB_EXPORT JKQTBasePlotter: public QObject {
         QAction* actCopyMatlab;
         /** \brief QAction which triggers the saving as PDF */
         QAction* actSavePDF;
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-        /** \brief QAction which triggers the saving as PostScript */
-        QAction* actSavePS;
-#endif
         /** \brief QAction which triggers the saving as pixel image */
         QAction* actSavePix;
         /** \brief QAction which triggers the saving as Scalable Vector Graphics (SVG) */
diff --git a/lib/jkqtplotter/jkqtpcoordinateaxes.cpp b/lib/jkqtplotter/jkqtpcoordinateaxes.cpp
index 51771e5da4..e910812db6 100644
--- a/lib/jkqtplotter/jkqtpcoordinateaxes.cpp
+++ b/lib/jkqtplotter/jkqtpcoordinateaxes.cpp
@@ -359,7 +359,7 @@ double JKQTPCoordinateAxis::calcLogTickSpacing() {
 
 QString JKQTPCoordinateAxis::floattolabel(double data) {
     int past_comma=axisStyle.labelDigits;
-    bool remove_trail0=true;
+    const bool remove_trail0=true;
     QLocale loc=QLocale::system();
     loc.setNumberOptions(QLocale::OmitGroupSeparator);
 
@@ -607,10 +607,10 @@ void JKQTPCoordinateAxis::saveCurrentAxisStyle(QSettings &settings, const QStrin
 }
 
 void JKQTPCoordinateAxis::setRange(double aamin, double aamax) {
-    double oldamin=axismin;
-    double oldamax=axismax;
-    double amin=aamin;
-    double amax=aamax;
+    const double oldamin=axismin;
+    const double oldamax=axismax;
+    double amin=std::min(aamin, aamax);
+    double amax=std::max(aamin, aamax);
     if (axisMinWidth>0 && fabs(amax-amin)<axisMinWidth) {
         amax=amin+axisMinWidth;
     }
@@ -621,10 +621,7 @@ void JKQTPCoordinateAxis::setRange(double aamin, double aamax) {
     if (amin<axisabsoultemin) axismin=axisabsoultemin;
     if (amax>axisabsoultemax) axismax=axisabsoultemax;
 
-    if (axismin>axismax) {
-        axismin=amax;
-        axismax=amin;
-    }
+
     if (isLogAxis()) {
         if (axismin<=0) axismin=1e-306;
         if (axismax<=0) axismax=1e-306;
@@ -950,21 +947,15 @@ void JKQTPCoordinateAxis::setTickLabelAngle(double __value) {
 
 
 void JKQTPCoordinateAxis::setAbsoluteRange(double amin, double amax) {
-    axisabsoultemin=amin;
-    axisabsoultemax=amax;
-
-    if (axisabsoultemin>axisabsoultemax) {
-        axisabsoultemin=amax;
-        axisabsoultemax=amin;
-    }
+    axisabsoultemin=std::min(amin, amax);
+    axisabsoultemax=std::max(amin, amax);
 
     if (axisabsoultemin==axisabsoultemax) {
         axisabsoultemax=axisabsoultemin+1;
     }
+
+    // ensure that the actual axis range is within the absolute range
     setRange(axismin, axismax);
-    /*paramsChanged=true;
-    calcPlotScaling();
-    redrawPlot();*/
 }
 
 double JKQTPCoordinateAxis::getNextLabelDistance(double x) {
@@ -1363,7 +1354,7 @@ void JKQTPVerticalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
     // plot thick axis at y==0
     if (axisStyle.showZeroAxis && (0>axismin) && (0<axismax)) {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPEnhancedPainter[%1]::drawAxes(): 0Axis").arg(objectName()));
+            JKQTPAutoOutputTimer jkaati(QString("JKQTPEnhancedPainter[%1]::drawAxes(): 0Axis").arg(objectName()));
         #endif
         QPen pmain1=pmain;
         pmain1.setWidthF(qMax(JKQTPlotterDrawingTools::ABS_MIN_LINEWIDTH, parent->pt2px(painter, axisStyle.lineWidthZeroAxis*parent->getLineWidthMultiplier())));
@@ -1399,7 +1390,7 @@ void JKQTPVerticalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
 
     {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPEnhancedPainter[%1]::drawAxes(): calcLabels").arg(objectName()));
+            JKQTPAutoOutputTimer jkaatii(QString("JKQTPEnhancedPainter[%1]::drawAxes(): calcLabels").arg(objectName()));
         #endif
         while (getNextLabel(x, label, first) && cnt<200) {
             double mtdist=getNextLabelDistance(x)/static_cast<double>(axisStyle.minorTicks+1);
@@ -1498,7 +1489,7 @@ void JKQTPVerticalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
     }
     {
     #ifdef JKQTBP_AUTOTIMER
-        JKQTPAutoOutputTimer jkaat(QString("JKQTPEnhancedPainter[%1]::drawAxes(): drawLines").arg(objectName()));
+        JKQTPAutoOutputTimer jkaati(QString("JKQTPEnhancedPainter[%1]::drawAxes(): drawLines").arg(objectName()));
     #endif
         painter.setPen(ptick);
         painter.drawLines(lines_ptick);
@@ -1511,7 +1502,7 @@ void JKQTPVerticalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
     // plot axis label
     if (!axisLabel.isEmpty() && JKQTPCADrawModeHasAxisLabel(axisStyle.drawMode1)) {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPEnhancedPainter[%1]::drawAxes(): axisLabel1").arg(objectName()));
+            JKQTPAutoOutputTimer jkaati(QString("JKQTPEnhancedPainter[%1]::drawAxes(): axisLabel1").arg(objectName()));
         #endif
         getParentMathText()->setFontSize(axisStyle.labelFontSize*parent->getFontSizeMultiplier());
         getParentMathText()->setFontRomanOrSpecial(getParent()->getCurrentPlotterStyle().defaultFontName);
@@ -1553,7 +1544,7 @@ void JKQTPVerticalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
     }
     if (!axisLabel.isEmpty() && JKQTPCADrawModeHasAxisLabel(axisStyle.drawMode2)) {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPEnhancedPainter[%1]::drawAxes(): axisLabel2").arg(objectName()));
+            JKQTPAutoOutputTimer jkaati(QString("JKQTPEnhancedPainter[%1]::drawAxes(): axisLabel2").arg(objectName()));
         #endif
         getParentMathText()->setFontSize(axisStyle.labelFontSize*parent->getFontSizeMultiplier());
         getParentMathText()->setFontRomanOrSpecial(getParent()->getCurrentPlotterStyle().defaultFontName);
@@ -1992,7 +1983,7 @@ void JKQTPHorizontalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
 
     {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPHorizontalAxis[%1]::drawAxes(): calcLabels").arg(objectName()));
+            JKQTPAutoOutputTimer jkaati(QString("JKQTPHorizontalAxis[%1]::drawAxes(): calcLabels").arg(objectName()));
         #endif
 
         while (getNextLabel(x, label, first) && cnt<200) {
@@ -2094,7 +2085,7 @@ void JKQTPHorizontalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
     }
     {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPHorizontalAxis[%1]::drawAxes(): drawLines").arg(objectName()));
+            JKQTPAutoOutputTimer jkaati(QString("JKQTPHorizontalAxis[%1]::drawAxes(): drawLines").arg(objectName()));
         #endif
 
         painter.setPen(ptick);
@@ -2108,7 +2099,7 @@ void JKQTPHorizontalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
     // plot axis label
     if (!axisLabel.isEmpty() && JKQTPCADrawModeHasAxisLabel(axisStyle.drawMode1)) {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPHorizontalAxis[%1]::drawAxes(): axisLabel1").arg(objectName()));
+            JKQTPAutoOutputTimer jkaati(QString("JKQTPHorizontalAxis[%1]::drawAxes(): axisLabel1").arg(objectName()));
         #endif
         getParentMathText()->setFontSize(axisStyle.labelFontSize*parent->getFontSizeMultiplier());
         getParentMathText()->setFontRomanOrSpecial(getParent()->getCurrentPlotterStyle().defaultFontName);
@@ -2149,7 +2140,7 @@ void JKQTPHorizontalAxis::drawAxes(JKQTPEnhancedPainter& painter) {
     }
     if (!axisLabel.isEmpty() && JKQTPCADrawModeHasAxisLabel(axisStyle.drawMode2)) {
         #ifdef JKQTBP_AUTOTIMER
-            JKQTPAutoOutputTimer jkaat(QString("JKQTPHorizontalAxis[%1]::drawAxes(): axisLabel2").arg(objectName()));
+            JKQTPAutoOutputTimer jkaati(QString("JKQTPHorizontalAxis[%1]::drawAxes(): axisLabel2").arg(objectName()));
         #endif
         getParentMathText()->setFontSize(axisStyle.labelFontSize*parent->getFontSizeMultiplier());
         getParentMathText()->setFontRomanOrSpecial(getParent()->getCurrentPlotterStyle().defaultFontName);
diff --git a/lib/jkqtplotter/jkqtpdatastorage.cpp b/lib/jkqtplotter/jkqtpdatastorage.cpp
index 5c637f7249..3ec5da5a4a 100644
--- a/lib/jkqtplotter/jkqtpdatastorage.cpp
+++ b/lib/jkqtplotter/jkqtpdatastorage.cpp
@@ -80,13 +80,11 @@ size_t JKQTPColumn::getRows() const {
 ////////////////////////////////////////////////////////////////////////////////////////////////
 void JKQTPColumn::copyData(QVector<double> &copyTo) const
 {
-    const double* d=getPointer(0);
-    copyTo.clear();
-    size_t i, cnt=getRows();
+    const size_t cnt=getRows();
     if (cnt>0) {
         copyTo.resize(static_cast<int>(cnt));
-        for (i=0; i<cnt; i++) {
-            copyTo[static_cast<int>(i)]=d[i];
+        for (size_t i=0; i<cnt; i++) {
+            copyTo[static_cast<int>(i)]=getValue(i);
         }
     }
 }
@@ -143,7 +141,7 @@ void JKQTPColumn::subtract(double value)
 {
     if (!datastore) return ;
     double* data=getPointer();
-    size_t N=getRows();
+    const size_t N=getRows();
     if (data){
         for (size_t i=0; i<N; i++) {
             data[i]=data[i]-value;
@@ -202,7 +200,7 @@ JKQTPDatastoreItem::JKQTPDatastoreItem(size_t columns, size_t rows){
         this->dataformat=JKQTPDatastoreItemFormat::SingleColumn;
         this->storageType=StorageType::Vector;
         datavec.resize(static_cast<int>(columns*rows));
-        for( double& d: datavec) { d=0.0; }
+        std::fill(datavec.begin(), datavec.end(), 0.0);
         this->data=datavec.data();
     }
     this->columns=columns;
@@ -562,7 +560,7 @@ size_t JKQTPDatastore::addCopiedItem(JKQTPDatastoreItemFormat dataformat, double
                 it->set(c, r, data[c*rows+r]);
             }
         }
-    } else if (dataformat==JKQTPDatastoreItemFormat::MatrixColumn) {
+    } else if (dataformat==JKQTPDatastoreItemFormat::MatrixRow) {
         it=new JKQTPDatastoreItem(columnsnum, rows);
         for (size_t r=0; r<rows; r++) {
             for (size_t c=0; c<columnsnum; c++) {
@@ -1033,8 +1031,8 @@ void JKQTPDatastore::saveMatlab(QTextStream &txt, const QSet<int>& userColumns)
             varnames.insert(newvar);
             txt<<QString("% data from columne %1 ('%2')\n").arg(col+1).arg(it.value().getName());
             txt<<QString("%1 = [ ").arg(newvar);
-            for (size_t i=0; i<it.value().getRows(); i++) {
-                txt<<loc.toString(get(it.key(), i))<<" ";
+            for (size_t rr=0; rr<it.value().getRows(); rr++) {
+                txt<<loc.toString(get(it.key(), rr))<<" ";
 
             }
             txt<<"];\n\n";
@@ -1072,8 +1070,7 @@ void JKQTPDatastore::saveCSV(QTextStream& txt, const QSet<int>& userColumns, con
         }
         txt<<"\n";
     }
-    size_t rows=getMaxRows();
-    for (size_t i=0; i<rows; i++) {
+    for (size_t i=0; i<getMaxRows(); i++) {
         bool first=true;
         QMapIterator<size_t, JKQTPColumn> it(columns);
         int j=0;
@@ -1127,15 +1124,14 @@ void JKQTPDatastore::saveSYLK(const QString& filename, const QSet<int>& userColu
 
 
 
-    size_t rows=getMaxRows();
-    for (size_t i=0; i<rows; i++) {
+    for (size_t rr=0; rr<getMaxRows(); rr++) {
         QMapIterator<size_t, JKQTPColumn> it(columns);
         c=1;
         while (it.hasNext()) {
             it.next();
-            if (userColumns.isEmpty() || userColumns.contains(static_cast<int>(i))) {
-                if (it.value().getRows()>i) {
-                    txt<<QString("C;X%1;Y%2;N;K%3\n").arg(c).arg(i+2).arg(get(it.key(), i));
+            if (userColumns.isEmpty() || userColumns.contains(static_cast<int>(rr))) {
+                if (it.value().getRows()>rr) {
+                    txt<<QString("C;X%1;Y%2;N;K%3\n").arg(c).arg(rr+2).arg(get(it.key(), rr));
                 }
                 c++;
             }
@@ -1202,7 +1198,7 @@ void JKQTPDatastore::saveDIF(const QString& filename, const QSet<int>& userColum
     if (!f.open(QIODevice::WriteOnly|QIODevice::Text)) return;
     QTextStream txt(&f);
     txt.setLocale(loc);
-    size_t rows=getMaxRows();
+    const size_t rows=getMaxRows();
 
     // write DIF header
     txt<<QString("TABLE\n0,1\n\"\"\n");