diff --git a/lib/jkqtplotter/graphs/jkqtpbarchart.cpp b/lib/jkqtplotter/graphs/jkqtpbarchart.cpp
index 0773fe7775..dba91e1960 100644
--- a/lib/jkqtplotter/graphs/jkqtpbarchart.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpbarchart.cpp
@@ -53,27 +53,17 @@ void JKQTPBarVerticalGraph::draw(JKQTPEnhancedPainter& painter) {
     JKQTPAutoOutputTimer jkaaot("JKQTPBarHorizontalGraph::draw");
 #endif
     if (parent==nullptr) return;
-    JKQTPDatastore* datastore=parent->getDatastore();
+    const JKQTPDatastore* datastore=parent->getDatastore();
     if (datastore==nullptr) return;
 
     drawErrorsBefore(painter);
 
-    QPen p=getLinePenForRects(painter, parent);
+    const QPen p=getLinePenForRects(painter, parent);
+    const QBrush b=getFillBrush(painter, parent);
 
-    QBrush b=getFillBrush(painter, parent);
-
-    int imax=static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
+    int imax=0;
     int imin=0;
-
-    if (imax<imin) {
-        int h=imin;
-        imin=imax;
-        imax=h;
-    }
-    if (imin<0) imin=0;
-    if (imax<0) imax=0;
-
-    {
+    if (getIndexRange(imin, imax)) {
         painter.save(); auto __finalpaint=JKQTPFinally([&painter]() {painter.restore();});
 
     //    double x0=transformX(0);
@@ -87,9 +77,9 @@ void JKQTPBarVerticalGraph::draw(JKQTPEnhancedPainter& painter) {
         const bool hasStackPar=hasStackParent();
         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));
-            int sr=datastore->getNextLowerIndex(xColumn, i);
-            int lr=datastore->getNextHigherIndex(xColumn, i);
+            const double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i));
+            const int sr=datastore->getNextLowerIndex(xColumn, i);
+            const int lr=datastore->getNextHigherIndex(xColumn, i);
             double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
             double yv0=y0;
             if (!qFuzzyIsNull(getBaseline())) yv0=transformY(getBaseline());
@@ -114,9 +104,9 @@ void JKQTPBarVerticalGraph::draw(JKQTPEnhancedPainter& painter) {
             delta=deltap+deltam;
 
             if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)) {
-                double x=transformX(xv+shift*delta-width*deltam);
+                const double x=transformX(xv+shift*delta-width*deltam);
                 double y=transformY(yv);
-                double xx=transformX(xv+shift*delta+width*deltap);
+                const double xx=transformX(xv+shift*delta+width*deltap);
                 double yy=yv0;
 
                 //std::cout<<"delta="<<delta<<"   x="<<x<<" y="<<y<<"   xx="<<xx<<" yy="<<yy<<std::endl;
@@ -239,83 +229,76 @@ void JKQTPBarHorizontalGraph::draw(JKQTPEnhancedPainter& painter) {
     JKQTPAutoOutputTimer jkaaot("JKQTPBarVerticalGraph::draw");
 #endif
     if (parent==nullptr) return;
-    JKQTPDatastore* datastore=parent->getDatastore();
+    const JKQTPDatastore* datastore=parent->getDatastore();
     if (datastore==nullptr) return;
 
     drawErrorsBefore(painter);
 
-    QPen p=getLinePenForRects(painter, parent);
+    const QPen p=getLinePenForRects(painter, parent);
+    const QBrush b=getFillBrush(painter, parent);
 
-    QBrush b=getFillBrush(painter, parent);
-
-    int imax=static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
+    int imax=0;
     int imin=0;
-    if (imax<imin) {
-        int h=imin;
-        imin=imax;
-        imax=h;
-    }
-    if (imin<0) imin=0;
-    if (imax<0) imax=0;
+    if (getIndexRange(imin, imax)) {
 
-    double x0=transformX(0);
-    if (parent->getXAxis()->isLogAxis()) x0=transformX(parent->getXAxis()->getMin());
-//    double y0=transformY(0);
-//    if (parent->getYAxis()->isLogAxis()) y0=transformY(parent->getYAxis()->getMin());
-    {
-        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));
-            double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
-            int sr=datastore->getNextLowerIndex(yColumn, i);
-            int lr=datastore->getNextHigherIndex(yColumn, i);
-            double xv0=x0;
-            if (!qFuzzyIsNull(getBaseline())) xv0=transformX(getBaseline());
-            if (hasStackPar) {
-                double stackLastX=getParentStackedMax(i);
-                const double xvold=xv;
-                xv0=transformX(stackLastX)+(getLineWidth());
-                xv=stackLastX+xvold;
-            }
+        double x0=transformX(0);
+        if (parent->getXAxis()->isLogAxis()) x0=transformX(parent->getXAxis()->getMin());
+    //    double y0=transformY(0);
+    //    if (parent->getYAxis()->isLogAxis()) y0=transformY(parent->getYAxis()->getMin());
+        {
+            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));
+                double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
+                int sr=datastore->getNextLowerIndex(yColumn, i);
+                int lr=datastore->getNextHigherIndex(yColumn, i);
+                double xv0=x0;
+                if (!qFuzzyIsNull(getBaseline())) xv0=transformX(getBaseline());
+                if (hasStackPar) {
+                    double stackLastX=getParentStackedMax(i);
+                    const double xvold=xv;
+                    xv0=transformX(stackLastX)+(getLineWidth());
+                    xv=stackLastX+xvold;
+                }
 
 
-            if (sr<0 && lr<0) { // only one y-value
-                deltam=0.5;
-                deltap=0.5;
-            } else if (lr<0) { // the right-most y-value
-                deltap=deltam=fabs(yv-datastore->get(yColumn,sr))/2.0;
-            } else if (sr<0) { // the left-most y-value
-                deltam=deltap=fabs(datastore->get(yColumn,lr)-yv)/2.0;
-            } else {
-                deltam=fabs(yv-datastore->get(yColumn,sr))/2.0;
-                deltap=fabs(datastore->get(yColumn,lr)-yv)/2.0;
-            }
-            delta=deltap+deltam;
+                if (sr<0 && lr<0) { // only one y-value
+                    deltam=0.5;
+                    deltap=0.5;
+                } else if (lr<0) { // the right-most y-value
+                    deltap=deltam=fabs(yv-datastore->get(yColumn,sr))/2.0;
+                } else if (sr<0) { // the left-most y-value
+                    deltam=deltap=fabs(datastore->get(yColumn,lr)-yv)/2.0;
+                } else {
+                    deltam=fabs(yv-datastore->get(yColumn,sr))/2.0;
+                    deltap=fabs(datastore->get(yColumn,lr)-yv)/2.0;
+                }
+                delta=deltap+deltam;
 
-            if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)) {
-                double x=xv0;
-                if (!qFuzzyIsNull(getBaseline())) x=transformX(getBaseline());
-                double y=transformY(yv+shift*delta+width*deltap);
-                double xx=transformX(xv);
-                double yy=transformY(yv+shift*delta-width*deltam);
-                if (x>xx) { qSwap(x,xx); }
-                //qDebug()<<"delta="<<delta<<"   x="<<x<<" y="<<y<<"   xx="<<xx<<" yy="<<yy;
-                //qDebug()<<"xv="<<xv<<"   x0="<<x0<<"   x="<<x<<"..."<<xx;
-                if (JKQTPIsOKFloat(x) && JKQTPIsOKFloat(xx) && JKQTPIsOKFloat(y) && JKQTPIsOKFloat(yy)) {
-                    painter.setBrush(b);
-                    painter.setPen(p);
-                    QRectF r(QPointF(x, y), QPointF(xx, yy));
-                    painter.drawRect(r);
+                if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)) {
+                    double x=xv0;
+                    if (!qFuzzyIsNull(getBaseline())) x=transformX(getBaseline());
+                    double y=transformY(yv+shift*delta+width*deltap);
+                    double xx=transformX(xv);
+                    double yy=transformY(yv+shift*delta-width*deltam);
+                    if (x>xx) { qSwap(x,xx); }
+                    //qDebug()<<"delta="<<delta<<"   x="<<x<<" y="<<y<<"   xx="<<xx<<" yy="<<yy;
+                    //qDebug()<<"xv="<<xv<<"   x0="<<x0<<"   x="<<x<<"..."<<xx;
+                    if (JKQTPIsOKFloat(x) && JKQTPIsOKFloat(xx) && JKQTPIsOKFloat(y) && JKQTPIsOKFloat(yy)) {
+                        painter.setBrush(b);
+                        painter.setPen(p);
+                        QRectF r(QPointF(x, y), QPointF(xx, yy));
+                        painter.drawRect(r);
+                    }
                 }
             }
         }
-
     }
     drawErrorsAfter(painter);
 }
@@ -363,33 +346,29 @@ bool JKQTPBarHorizontalErrorGraph::getXMinMax(double &minx, double &maxx, double
 
         if (parent==nullptr) return false;
 
-        JKQTPDatastore* datastore=parent->getDatastore();
+        const JKQTPDatastore* datastore=parent->getDatastore();
+        int imax=0;
         int imin=0;
-        int imax=static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
+        if (getIndexRange(imin, imax)) {
 
-        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) ) {
-                if (start || xv>maxx) maxx=xv;
-                if (start || xv<minx) minx=xv;
-                xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
-                if (xvv>maxx) maxx=xvv;
-                if (xvv<minx) minx=xvv;
-                xvsgz=xvv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
+            for (int i=imin; i<imax; i++) {
+                double xvsgz;
+                const double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))+getXErrorU(i, datastore);
+                const double xvv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i))-getXErrorL(i, datastore);
+                if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(xvv) ) {
+                    if (start || xv>maxx) maxx=xv;
+                    if (start || xv<minx) minx=xv;
+                    xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                    if (xvv>maxx) maxx=xvv;
+                    if (xvv<minx) minx=xvv;
+                    xvsgz=xvv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
             }
+            return !start;
         }
-        return !start;
+        return false;
     }
 }
 
@@ -465,33 +444,29 @@ bool JKQTPBarVerticalErrorGraph::getYMinMax(double &miny, double &maxy, double &
         if (parent==nullptr) return false;
 
         JKQTPDatastore* datastore=parent->getDatastore();
+        int imax=0;
         int imin=0;
-        int imax=static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
+        if (getIndexRange(imin, imax)) {
 
-        for (int i=imin; i<imax; i++) {
-            double yv=getBaseline();
-            if (JKQTPIsOKFloat(yv)) {
-                if (yv>maxy) maxy=yv;
-                if (yv<miny) miny=yv;
-                double xvsgz;
-                xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
-            }
-            yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
-            if (JKQTPIsOKFloat(yv)) {
-                if (yv>maxy) maxy=yv;
-                if (yv<miny) miny=yv;
-                double xvsgz;
-                xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+
+            for (int i=imin; i<imax; i++) {
+                double yv=getBaseline();
+                if (JKQTPIsOKFloat(yv)) {
+                    if (yv>maxy) maxy=yv;
+                    if (yv<miny) miny=yv;
+                    double xvsgz;
+                    xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                }
+                yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
+                if (JKQTPIsOKFloat(yv)) {
+                    if (yv>maxy) maxy=yv;
+                    if (yv<miny) miny=yv;
+                    double xvsgz;
+                    xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                }
             }
+            return true;
         }
-        return true;
     } else {
         bool start=false;
         miny=getBaseline();
@@ -505,34 +480,30 @@ bool JKQTPBarVerticalErrorGraph::getYMinMax(double &miny, double &maxy, double &
 
         if (parent==nullptr) return false;
 
-        JKQTPDatastore* datastore=parent->getDatastore();
+        const JKQTPDatastore* datastore=parent->getDatastore();
+        int imax=0;
         int imin=0;
-        int imax=static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
+        if (getIndexRange(imin, imax)) {
 
 
-        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) ) {
-                if (start || yv>maxy) maxy=yv;
-                if (start || yv<miny) miny=yv;
-                double xvsgz;
-                xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
-                if (start || yvv>maxy) maxy=yvv;
-                if (start || yvv<miny) miny=yvv;
-                xvsgz=yvv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
+            for (int i=imin; i<imax; i++) {
+                const double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))+getYErrorU(i, datastore);
+                const double yvv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i))-getYErrorL(i, datastore);
+                if (JKQTPIsOKFloat(yv) && JKQTPIsOKFloat(yvv) ) {
+                    if (start || yv>maxy) maxy=yv;
+                    if (start || yv<miny) miny=yv;
+                    double xvsgz;
+                    xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                    if (start || yvv>maxy) maxy=yvv;
+                    if (start || yvv<miny) miny=yvv;
+                    xvsgz=yvv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
             }
+            return !start;
         }
-        return !start;
     }
+    return false;
 }
 
 int JKQTPBarVerticalErrorGraph::getBarErrorColumn() const
diff --git a/lib/jkqtplotter/graphs/jkqtpimpulses.cpp b/lib/jkqtplotter/graphs/jkqtpimpulses.cpp
index 7a24469f51..f7c4506ed4 100644
--- a/lib/jkqtplotter/graphs/jkqtpimpulses.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpimpulses.cpp
@@ -93,55 +93,39 @@ void JKQTPImpulsesHorizontalGraph::draw(JKQTPEnhancedPainter& painter) {
         QPen p=getLinePen(painter, parent);
         p.setCapStyle(Qt::FlatCap);
 
-        int imax=static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
+        int imax=0;
         int imin=0;
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
+        if (getIndexRange(imin, imax)) {
 
-        //double xold=-1;
-        //double yold=-1;
-        double x0=transformX(getBaseline());
-        if (parent->getXAxis()->isLogAxis()) {
-            if (getBaseline()>0 && getBaseline()>parent->getXAxis()->getMin()) x0=transformX(getBaseline());
-            else x0=transformX(parent->getXAxis()->getMin());
-        }
-    //    double y0=transformY(getBaseline());
-    //    if (parent->getYAxis()->isLogAxis()) {
-    //        y0=transformY(parent->getYAxis()->getMin());
-    //        if (getBaseline()>0 && getBaseline()>parent->getYAxis()->getMin()) y0=transformY(getBaseline());
-    //        else y0=transformY(parent->getYAxis()->getMin());
-    //    }
-        //bool first=false;
-        QVector<QLineF> lines;
-        QVector<QPointF> points;
-        intSortData();
-        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));
-            double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
-            if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)) {
-                double x=transformX(xv);
-                double y=transformY(yv);
-
-
-                lines.append(QLineF(x0, y, x, y));
-                points.append(QPointF(x,y));
-    //            xold=x;
-    //            yold=y;
-                //first=true;
+            double x0=transformX(getBaseline());
+            if (parent->getXAxis()->isLogAxis()) {
+                if (getBaseline()>0 && getBaseline()>parent->getXAxis()->getMin()) x0=transformX(getBaseline());
+                else x0=transformX(parent->getXAxis()->getMin());
             }
-        }
-        painter.setPen(p);
-        if (lines.size()>0) painter.drawLines(lines);
-        if (drawSymbols && points.size()>0) {
-            painter.save(); auto __finalpaintsym=JKQTPFinally([&painter]() {painter.restore();});
-            for (auto& p: points) {
-                plotStyledSymbol(parent, painter, p.x(), p.y());
+
+            QVector<QLineF> lines;
+            QVector<QPointF> points;
+            intSortData();
+            for (int iii=imin; iii<imax; iii++) {
+                const int i=qBound(imin, getDataIndex(iii), imax);
+                const double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i));
+                const double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
+                if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)) {
+                    const double x=transformX(xv);
+                    const double y=transformY(yv);
+
+                    lines.append(QLineF(x0, y, x, y));
+                    points.append(QPointF(x,y));
+
+                }
+            }
+            painter.setPen(p);
+            if (lines.size()>0) painter.drawLines(lines);
+            if (drawSymbols && points.size()>0) {
+                painter.save(); auto __finalpaintsym=JKQTPFinally([&painter]() {painter.restore();});
+                for (auto& p: points) {
+                    plotStyledSymbol(parent, painter, p.x(), p.y());
+                }
             }
         }
 
@@ -210,55 +194,42 @@ void JKQTPImpulsesVerticalGraph::draw(JKQTPEnhancedPainter& painter) {
         QPen p=getLinePen(painter, parent);
         p.setCapStyle(Qt::FlatCap);
 
-        int imax=static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
+        int imax=0;
         int imin=0;
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
-
-        //double xold=-1;
-        //double yold=-1;
-        //bool first=false;
-    //    double x0=transformX(getBaseline());
-    //    if (parent->getXAxis()->isLogAxis()) {
-    //        if (getBaseline()>0 && getBaseline()>parent->getXAxis()->getMin()) x0=transformX(getBaseline());
-    //        else x0=transformX(parent->getXAxis()->getMin());
-    //    }
-        double y0=transformY(getBaseline());
-        if (parent->getYAxis()->isLogAxis()) {
-            y0=transformY(parent->getYAxis()->getMin());
-            if (getBaseline()>0 && getBaseline()>parent->getYAxis()->getMin()) y0=transformY(getBaseline());
-            else y0=transformY(parent->getYAxis()->getMin());
-        }
-        QVector<QLineF> lines;
-        QVector<QPointF> points;
-        intSortData();
-        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));
-            double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
-            if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv) ) {
-                double x=transformX(xv);
-                double y=transformY(yv);
+        if (getIndexRange(imin, imax)) {
 
 
-                lines.append(QLineF(x, y0, x, y));
-                points.append(QPointF(x,y));
-                //xold=x;
-                //yold=y;
-                //first=true;
+
+            double y0=transformY(getBaseline());
+            if (parent->getYAxis()->isLogAxis()) {
+                y0=transformY(parent->getYAxis()->getMin());
+                if (getBaseline()>0 && getBaseline()>parent->getYAxis()->getMin()) y0=transformY(getBaseline());
+                else y0=transformY(parent->getYAxis()->getMin());
             }
-        }
-        painter.setPen(p);
-        if (lines.size()>0) painter.drawLines(lines);
-        if (drawSymbols && points.size()>0) {
-            painter.save(); auto __finalpaintsym=JKQTPFinally([&painter]() {painter.restore();});
-            for (auto& p: points) {
-                plotStyledSymbol(parent, painter, p.x(), p.y());
+            QVector<QLineF> lines;
+            QVector<QPointF> points;
+            intSortData();
+            for (int iii=imin; iii<imax; iii++) {
+                const int i=qBound(imin, getDataIndex(iii), imax);
+                const double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i));
+                const double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
+                if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv) ) {
+                    const double x=transformX(xv);
+                    const double y=transformY(yv);
+
+
+                    lines.append(QLineF(x, y0, x, y));
+                    points.append(QPointF(x,y));
+
+                }
+            }
+            painter.setPen(p);
+            if (lines.size()>0) painter.drawLines(lines);
+            if (drawSymbols && points.size()>0) {
+                painter.save(); auto __finalpaintsym=JKQTPFinally([&painter]() {painter.restore();});
+                for (auto& p: points) {
+                    plotStyledSymbol(parent, painter, p.x(), p.y());
+                }
             }
         }
     }
diff --git a/lib/jkqtplotter/graphs/jkqtpscatter.cpp b/lib/jkqtplotter/graphs/jkqtpscatter.cpp
index f1427d9fef..b79edc825e 100644
--- a/lib/jkqtplotter/graphs/jkqtpscatter.cpp
+++ b/lib/jkqtplotter/graphs/jkqtpscatter.cpp
@@ -61,7 +61,7 @@ void JKQTPXYLineGraph::draw(JKQTPEnhancedPainter& painter) {
     JKQTPAutoOutputTimer jkaaot("JKQTPXYLineGraph::draw");
 #endif
     if (parent==nullptr) return;
-    JKQTPDatastore* datastore=parent->getDatastore();
+    const JKQTPDatastore* datastore=parent->getDatastore();
     if (datastore==nullptr) return;
 
     //qDebug()<<"JKQTPXYLineGraph::draw();";
@@ -72,63 +72,56 @@ void JKQTPXYLineGraph::draw(JKQTPEnhancedPainter& painter) {
         painter.save(); auto __finalpaint=JKQTPFinally([&painter]() {painter.restore();});
         //qDebug()<<"JKQTPXYLineGraph::draw(): "<<2;
 
-        QPen p=getLinePen(painter, parent);
+        const QPen p=getLinePen(painter, parent);
+        const QPen penSelection=getHighlightingLinePen(painter, parent);
 
 
-        QPen penSelection=getHighlightingLinePen(painter, parent);
-
-
-        int imax= static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
+        int imax=0;
         int imin=0;
+        if (getIndexRange(imin, imax)) {
 
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
 
-        std::vector<QPolygonF> vec_linesP;
-        vec_linesP.push_back(QPolygonF());
-        intSortData();
-        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));
-            double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
-            double x=transformX(xv);
-            double y=transformY(yv);
-            //qDebug()<<"JKQTPXYLineGraph::draw(): (xv, yv) =    ( "<<xv<<", "<<yv<<" )";
-            if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)  &&  JKQTPIsOKFloat(x) && JKQTPIsOKFloat(y)) {
+            std::vector<QPolygonF> vec_linesP;
+            vec_linesP.push_back(QPolygonF());
+            intSortData();
+            for (int iii=imin; iii<imax; iii++) {
+                const int i=qBound(imin, getDataIndex(iii), imax);
+                const double xv=datastore->get(static_cast<size_t>(xColumn),static_cast<size_t>(i));
+                const double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
+                const double x=transformX(xv);
+                const double y=transformY(yv);
+                //qDebug()<<"JKQTPXYLineGraph::draw(): (xv, yv) =    ( "<<xv<<", "<<yv<<" )";
+                if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)  &&  JKQTPIsOKFloat(x) && JKQTPIsOKFloat(y)) {
 
-                if (isHighlighted() && getSymbolType()!=JKQTPNoSymbol) {
-                    //JKQTPPlotSymbol(painter, x, y, JKQTPFilledCircle, parent->pt2px(painter, symbolSize*1.5), parent->pt2px(painter, symbolWidth*parent->getLineWidthMultiplier()), penSelection.color(), penSelection.color());
-                }
-                if ((!parent->getXAxis()->isLogAxis() || xv>0.0) && (!parent->getYAxis()->isLogAxis() || yv>0.0) ) {
-                    plotStyledSymbol(parent, painter, x, y);
-                    if (drawLine) {
-                        vec_linesP[vec_linesP.size()-1] << QPointF(x,y);
+                    if (isHighlighted() && getSymbolType()!=JKQTPNoSymbol) {
+                        //JKQTPPlotSymbol(painter, x, y, JKQTPFilledCircle, parent->pt2px(painter, symbolSize*1.5), parent->pt2px(painter, symbolWidth*parent->getLineWidthMultiplier()), penSelection.color(), penSelection.color());
+                    }
+                    if ((!parent->getXAxis()->isLogAxis() || xv>0.0) && (!parent->getYAxis()->isLogAxis() || yv>0.0) ) {
+                        plotStyledSymbol(parent, painter, x, y);
+                        if (drawLine) {
+                            vec_linesP[vec_linesP.size()-1] << QPointF(x,y);
+                        }
+                    } else {
+                        vec_linesP.push_back(QPolygonF());
                     }
-                } else {
-                    vec_linesP.push_back(QPolygonF());
                 }
             }
-        }
-        //qDebug()<<"JKQTPXYLineGraph::draw(): "<<4<<" lines="<<lines.size();
-        //qDebug()<<"JKQTPXYLineGraph::draw(): "<<5<<"  p="<<painter.pen();
-        for (auto &linesP : vec_linesP) {
-            if (linesP.size()>0) {
-                if (isHighlighted()) {
-                    painter.setPen(penSelection);
+            //qDebug()<<"JKQTPXYLineGraph::draw(): "<<4<<" lines="<<lines.size();
+            //qDebug()<<"JKQTPXYLineGraph::draw(): "<<5<<"  p="<<painter.pen();
+            for (auto &linesP : vec_linesP) {
+                if (linesP.size()>0) {
+                    if (isHighlighted()) {
+                        painter.setPen(penSelection);
+                        //painter.drawLines(lines);
+                        painter.drawPolyline(linesP);
+                    }
+                    painter.setPen(p);
                     //painter.drawLines(lines);
                     painter.drawPolyline(linesP);
                 }
-                painter.setPen(p);
-                //painter.drawLines(lines);
-                painter.drawPolyline(linesP);
             }
+            //qDebug()<<"JKQTPXYLineGraph::draw(): "<<6;
         }
-        //qDebug()<<"JKQTPXYLineGraph::draw(): "<<6;
     }
     //qDebug()<<"JKQTPXYLineGraph::draw(): "<<7;
     drawErrorsAfter(painter);
@@ -205,36 +198,30 @@ bool JKQTPXYLineErrorGraph::getXMinMax(double &minx, double &maxx, double &small
 
         if (parent==nullptr) return false;
 
-        JKQTPDatastore* datastore=parent->getDatastore();
+        const JKQTPDatastore* datastore=parent->getDatastore();
+        int imax=0;
         int imin=0;
-        int imax= static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
-
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
-
-        for (int i=imin; i<imax; i++) {
-            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;
-                const double xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
-            }
-            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;
-                const double xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
+        if (getIndexRange(imin, imax)) {
+            for (int i=imin; i<imax; i++) {
+                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;
+                    const double xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
+                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;
+                    const double xvsgz=xv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
             }
+            return !start;
         }
-        return !start;
     }
+    return false;
 }
 
 bool JKQTPXYLineErrorGraph::getYMinMax(double &miny, double &maxy, double &smallestGreaterZero) {
@@ -248,36 +235,30 @@ bool JKQTPXYLineErrorGraph::getYMinMax(double &miny, double &maxy, double &small
 
         if (parent==nullptr) return false;
 
-        JKQTPDatastore* datastore=parent->getDatastore();
+        const JKQTPDatastore* datastore=parent->getDatastore();
+        int imax=0;
         int imin=0;
-        int imax= static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
-
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        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);
-            if (JKQTPIsOKFloat(yv)) {
-                if (start || yv>maxy) maxy=yv;
-                if (start || yv<miny) miny=yv;
-                const double xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
-            }
-            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;
-                const double xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
+        if (getIndexRange(imin, imax)) {
+            for (int i=imin; i<imax; i++) {
+                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;
+                    const double xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
+                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;
+                    const double xvsgz=yv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
             }
+            return !start;
         }
-        return !start;
     }
+    return false;
 }
 
 bool JKQTPXYLineErrorGraph::usesColumn(int c) const
@@ -359,102 +340,109 @@ void JKQTPXYParametrizedScatterGraph::draw(JKQTPEnhancedPainter &painter)
 
     painter.save(); auto __finalpaint=JKQTPFinally([&painter]() {painter.restore();});
 
-    QPen p=getLinePen(painter, parent);
+    const QPen p=getLinePen(painter, parent);
+    const QPen penSelection=getHighlightingLinePen(painter, parent);
 
 
-    QPen penSelection=getHighlightingLinePen(painter, parent);
-
-
-    int imax= static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
+    int imax=0;
     int imin=0;
-    if (imax<imin) {
-        int h=imin;
-        imin=imax;
-        imax=h;
-    }
-    if (imin<0) imin=0;
-    if (imax<0) imax=0;
+    if (getIndexRange(imin, imax)) {
 
-    QVector<QLineF> lines;
-    QPolygonF linesP;
-    QVector<QColor> linecols;
-    QVector<QColor> linecolss;
-    QVector<double> linewidths;
-    //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));
-            double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
-            double x=transformX(xv);
-            double y=transformY(yv);
-            if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)  &&  JKQTPIsOKFloat(x) && JKQTPIsOKFloat(y)) {
-                double symbSize= parent->pt2px(painter, getLocalSymbolSize(i));
-                double lineW= parent->pt2px(painter, getLocalLineWidth(i));
+        QVector<QLineF> lines;
+        QPolygonF linesP;
+        QVector<QColor> linecols;
+        QVector<QColor> linecolss;
+        QVector<double> linewidths;
+        //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;
 
-                if (gridModeForSymbolSize) {
-                    if (!hasSpecSymbSize) {
-                        double sSX= fabs(transformX( xv+gridDeltaX*gridSymbolFractionSize/2.0)-transformX( xv-gridDeltaX*gridSymbolFractionSize/2.0));
-                        double sSY= fabs(transformY( yv+gridDeltaY*gridSymbolFractionSize/2.0)-transformY( yv-gridDeltaY*gridSymbolFractionSize/2.0));
-                        hasSpecSymbSize=true;
-                        specSymbSize=qMin(sSX,sSY);
+            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));
+                double yv=datastore->get(static_cast<size_t>(yColumn),static_cast<size_t>(i));
+                double x=transformX(xv);
+                double y=transformY(yv);
+                if (JKQTPIsOKFloat(xv) && JKQTPIsOKFloat(yv)  &&  JKQTPIsOKFloat(x) && JKQTPIsOKFloat(y)) {
+                    double symbSize= parent->pt2px(painter, getLocalSymbolSize(i));
+                    double lineW= parent->pt2px(painter, getLocalLineWidth(i));
+
+                    if (gridModeForSymbolSize) {
+                        if (!hasSpecSymbSize) {
+                            double sSX= fabs(transformX( xv+gridDeltaX*gridSymbolFractionSize/2.0)-transformX( xv-gridDeltaX*gridSymbolFractionSize/2.0));
+                            double sSY= fabs(transformY( yv+gridDeltaY*gridSymbolFractionSize/2.0)-transformY( yv-gridDeltaY*gridSymbolFractionSize/2.0));
+                            hasSpecSymbSize=true;
+                            specSymbSize=qMin(sSX,sSY);
+                        }
+                        symbSize=specSymbSize;
                     }
-                    symbSize=specSymbSize;
-                }
-                QColor symbColor=getLocalColor(i);
-                QColor symbFillColor=JKQTPGetDerivedColor(symbolFillDerivationMode, symbColor);
-                //qDebug()<<i<<symbolSize<<symbColor;
-                if (drawLine) {
-                    linesP<<QPointF(x,y);
-                }
-                if (first && drawLine) {
-                    double xl1=xold;
-                    double yl1=yold;
-                    double xl2=x;
-                    double yl2=y;
-
-                    if (isHighlighted()) {
-                        if (colorColumn>=0) linecolss<<symbColor.lighter();
-                        else linecolss<<getHighlightingLineColor();
+                    QColor symbColor=getLocalColor(i);
+                    QColor symbFillColor=JKQTPGetDerivedColor(symbolFillDerivationMode, symbColor);
+                    //qDebug()<<i<<symbolSize<<symbColor;
+                    if (drawLine) {
+                        linesP<<QPointF(x,y);
                     }
-                    linecols<<symbColor;
-                    lines<<QLineF(xl1, yl1, xl2, yl2);
-                    linewidths<<lineW;
-                }
+                    if (first && drawLine) {
+                        double xl1=xold;
+                        double yl1=yold;
+                        double xl2=x;
+                        double yl2=y;
 
-                if ((!parent->getXAxis()->isLogAxis() || xv>0.0) && (!parent->getYAxis()->isLogAxis() || yv>0.0) ) {
-                    if (isHighlighted() && getSymbolType()!=JKQTPNoSymbol && symbolColumn<0) {
-                        JKQTPPlotSymbol(painter, x, y, JKQTPFilledCircle,symbSize, parent->pt2px(painter, getSymbolLineWidth()*parent->getLineWidthMultiplier()), penSelection.color(), penSelection.color());
-                    } else {
-                        JKQTPPlotSymbol(painter, x, y, getLocalSymbolType(i), symbSize, parent->pt2px(painter, getSymbolLineWidth()*parent->getLineWidthMultiplier()), symbColor, symbFillColor);
+                        if (isHighlighted()) {
+                            if (colorColumn>=0) linecolss<<symbColor.lighter();
+                            else linecolss<<getHighlightingLineColor();
+                        }
+                        linecols<<symbColor;
+                        lines<<QLineF(xl1, yl1, xl2, yl2);
+                        linewidths<<lineW;
                     }
+
+                    if ((!parent->getXAxis()->isLogAxis() || xv>0.0) && (!parent->getYAxis()->isLogAxis() || yv>0.0) ) {
+                        if (isHighlighted() && getSymbolType()!=JKQTPNoSymbol && symbolColumn<0) {
+                            JKQTPPlotSymbol(painter, x, y, JKQTPFilledCircle,symbSize, parent->pt2px(painter, getSymbolLineWidth()*parent->getLineWidthMultiplier()), penSelection.color(), penSelection.color());
+                        } else {
+                            JKQTPPlotSymbol(painter, x, y, getLocalSymbolType(i), symbSize, parent->pt2px(painter, getSymbolLineWidth()*parent->getLineWidthMultiplier()), symbColor, symbFillColor);
+                        }
+                    }
+
+
+                    xold=x;
+                    yold=y;
+                    first=true;
                 }
-
-
-                xold=x;
-                yold=y;
-                first=true;
             }
         }
-    }
 
 
 
-    if (lines.size()>0) {
-        painter.save(); auto __finalpaintinner=JKQTPFinally([&painter]() {painter.restore();});
-        if (isHighlighted()) {
-            QPen pp=penSelection;
-            if (colorColumn>=0) {
+        if (lines.size()>0) {
+            painter.save(); auto __finalpaintinner=JKQTPFinally([&painter]() {painter.restore();});
+            if (isHighlighted()) {
+                QPen pp=penSelection;
+                if (colorColumn>=0) {
+                    for (int i=0; i<lines.size(); i++) {
+                        pp.setColor(linecolss.value(i, getHighlightingLineColor()));
+                        painter.setPen(pp);
+                        painter.drawLine(lines[i]);
+                    }
+                } else {
+                    pp.setColor(getHighlightingLineColor());
+                    painter.setPen(pp);
+                    painter.drawPolyline(linesP);
+                }
+            }
+            QPen pp=p;
+            if (colorColumn>=0 || linewidthColumn>=0) {
                 for (int i=0; i<lines.size(); i++) {
-                    pp.setColor(linecolss.value(i, getHighlightingLineColor()));
+                    pp.setColor(linecols.value(i, getLineColor()));
+                    pp.setWidthF(linewidths.value(i, parent->pt2px(painter, getLineWidth()*parent->getLineWidthMultiplier())));
                     painter.setPen(pp);
                     painter.drawLine(lines[i]);
                 }
@@ -463,21 +451,8 @@ void JKQTPXYParametrizedScatterGraph::draw(JKQTPEnhancedPainter &painter)
                 painter.setPen(pp);
                 painter.drawPolyline(linesP);
             }
-        }
-        QPen pp=p;
-        if (colorColumn>=0 || linewidthColumn>=0) {
-            for (int i=0; i<lines.size(); i++) {
-                pp.setColor(linecols.value(i, getLineColor()));
-                pp.setWidthF(linewidths.value(i, parent->pt2px(painter, getLineWidth()*parent->getLineWidthMultiplier())));
-                painter.setPen(pp);
-                painter.drawLine(lines[i]);
-            }
-        } else {
-            pp.setColor(getHighlightingLineColor());
-            painter.setPen(pp);
-            painter.drawPolyline(linesP);
-        }
 
+        }
     }
 
     drawErrorsAfter(painter);
@@ -897,36 +872,30 @@ bool JKQTPXYParametrizedErrorScatterGraph::getXMinMax(double &minx, double &maxx
 
         if (parent==nullptr) return false;
 
-        JKQTPDatastore* datastore=parent->getDatastore();
+        const JKQTPDatastore* datastore=parent->getDatastore();
+        int imax=0;
         int imin=0;
-        int imax= static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
-
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
-
-        for (int i=imin; i<imax; i++) {
-            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;
-                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;
-                const double xvsgz=xvv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
+        if (getIndexRange(imin, imax)) {
+            for (int i=imin; i<imax; i++) {
+                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;
+                    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;
+                    const double xvsgz=xvv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
             }
+            return !start;
         }
-        return !start;
     }
+    return false;
 }
 
 bool JKQTPXYParametrizedErrorScatterGraph::getYMinMax(double &miny, double &maxy, double &smallestGreaterZero)
@@ -941,36 +910,30 @@ bool JKQTPXYParametrizedErrorScatterGraph::getYMinMax(double &miny, double &maxy
 
         if (parent==nullptr) return false;
 
-        JKQTPDatastore* datastore=parent->getDatastore();
+        const JKQTPDatastore* datastore=parent->getDatastore();
+        int imax=0;
         int imin=0;
-        int imax= static_cast<int>(qMin(datastore->getRows(static_cast<size_t>(xColumn)), datastore->getRows(static_cast<size_t>(yColumn))));
-
-        if (imax<imin) {
-            int h=imin;
-            imin=imax;
-            imax=h;
-        }
-        if (imin<0) imin=0;
-        if (imax<0) imax=0;
-
-        for (int i=imin; i<imax; i++) {
-            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;
-                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;
-                const double xvsgz=yvv; SmallestGreaterZeroCompare_xvsgz();
-                start=false;
+        if (getIndexRange(imin, imax)) {
+            for (int i=imin; i<imax; i++) {
+                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;
+                    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;
+                    const double xvsgz=yvv; SmallestGreaterZeroCompare_xvsgz();
+                    start=false;
+                }
             }
+            return !start;
         }
-        return !start;
     }
+    return false;
 }
 
 bool JKQTPXYParametrizedErrorScatterGraph::usesColumn(int c) const
diff --git a/lib/jkqtplotter/jkqtpgraphsbaseerrors.cpp b/lib/jkqtplotter/jkqtpgraphsbaseerrors.cpp
index 81e2bac6db..b11333915b 100644
--- a/lib/jkqtplotter/jkqtpgraphsbaseerrors.cpp
+++ b/lib/jkqtplotter/jkqtpgraphsbaseerrors.cpp
@@ -623,7 +623,7 @@ void JKQTPXGraphErrorData::setXErrorColumnLower(int __value) {
 }
 
 
-double JKQTPXGraphErrorData::getXErrorU(int i, JKQTPDatastore *ds) const
+double JKQTPXGraphErrorData::getXErrorU(int i, const JKQTPDatastore *ds) const
 {
     if (ds && xErrorColumn>=0 && i>=0 && i<static_cast<int>(ds->getRows(xErrorColumn))) {
         return ds->get(xErrorColumn, static_cast<size_t>(i));
@@ -631,7 +631,7 @@ double JKQTPXGraphErrorData::getXErrorU(int i, JKQTPDatastore *ds) const
     return 0.0;
 }
 
-double JKQTPXGraphErrorData::getXErrorL(int i, JKQTPDatastore *ds) const
+double JKQTPXGraphErrorData::getXErrorL(int i, const JKQTPDatastore *ds) const
 {
     if (ds) {
         if (xErrorSymmetric) {
@@ -699,7 +699,7 @@ void JKQTPYGraphErrorData::setYErrorColumnLower(int __value) {
 }
 
 
-double JKQTPYGraphErrorData::getYErrorU(int i, JKQTPDatastore *ds) const
+double JKQTPYGraphErrorData::getYErrorU(int i, const JKQTPDatastore *ds) const
 {
     if (ds && yErrorColumn>=0 && i>=0 && i<static_cast<int>(ds->getRows(yErrorColumn))) {
         return ds->get(yErrorColumn, static_cast<size_t>(i));
@@ -707,7 +707,7 @@ double JKQTPYGraphErrorData::getYErrorU(int i, JKQTPDatastore *ds) const
     return 0.0;
 }
 
-double JKQTPYGraphErrorData::getYErrorL(int i, JKQTPDatastore *ds) const
+double JKQTPYGraphErrorData::getYErrorL(int i, const JKQTPDatastore *ds) const
 {
     if (ds) {
         if (yErrorSymmetric) {
@@ -735,7 +735,7 @@ bool JKQTPXGraphErrors::errorUsesColumn(int c) const
     return c==(xErrorColumn) || (c==xErrorColumnLower);
 }
 
-void JKQTPXGraphErrors::plotErrorIndicators(JKQTPEnhancedPainter& painter, JKQTBasePlotter* parent, JKQTPGraph *parentGraph, int xColumn, int yColumn, double xrelshift, double yrelshift, const  QVector<int>* dataorder) const {
+void JKQTPXGraphErrors::plotErrorIndicators(JKQTPEnhancedPainter& painter, const JKQTBasePlotter* parent, const JKQTPGraph *parentGraph, int xColumn, int yColumn, double xrelshift, double yrelshift, const  QVector<int>* dataorder) const {
     intPlotXYErrorIndicators(painter, parent, parentGraph, xColumn, yColumn, xErrorColumn, -1, xErrorStyle, JKQTPNoError, xErrorColumnLower, -1, xErrorSymmetric, true, xrelshift, yrelshift, dataorder);
 }
 
@@ -747,7 +747,7 @@ JKQTPYGraphErrors::JKQTPYGraphErrors()
 {
 }
 
-void JKQTPYGraphErrors::plotErrorIndicators(JKQTPEnhancedPainter& painter, JKQTBasePlotter* parent, JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift, double yrelshift, const  QVector<int>* dataorder) const {
+void JKQTPYGraphErrors::plotErrorIndicators(JKQTPEnhancedPainter& painter, const JKQTBasePlotter* parent, const JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift, double yrelshift, const  QVector<int>* dataorder) const {
     intPlotXYErrorIndicators(painter, parent, parentGraph, xColumn, yColumn, -1, yErrorColumn, JKQTPNoError, yErrorStyle, -1, yErrorColumnLower, true, yErrorSymmetric, xrelshift, yrelshift, dataorder);
 }
 
@@ -767,7 +767,7 @@ JKQTPXYGraphErrors::JKQTPXYGraphErrors()
 
 }
 
-void JKQTPXYGraphErrors::plotErrorIndicators(JKQTPEnhancedPainter& painter, JKQTBasePlotter* parent, JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift, double yrelshift, const  QVector<int>* dataorder) const {
+void JKQTPXYGraphErrors::plotErrorIndicators(JKQTPEnhancedPainter& painter, const JKQTBasePlotter* parent, const JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift, double yrelshift, const  QVector<int>* dataorder) const {
     this->intPlotXYErrorIndicators(painter, parent, parentGraph, xColumn, yColumn, xErrorColumn, yErrorColumn, xErrorStyle, yErrorStyle, xErrorColumnLower, yErrorColumnLower, xErrorSymmetric, yErrorSymmetric, xrelshift, yrelshift, dataorder);
 }
 
diff --git a/lib/jkqtplotter/jkqtpgraphsbaseerrors.h b/lib/jkqtplotter/jkqtpgraphsbaseerrors.h
index 31ca308026..4dbc1fd3f1 100644
--- a/lib/jkqtplotter/jkqtpgraphsbaseerrors.h
+++ b/lib/jkqtplotter/jkqtpgraphsbaseerrors.h
@@ -227,9 +227,9 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPXGraphErrorData  {
         JKQTPErrorPlotstyle xErrorStyle;
 
         /** \brief returns the upper x-error for the i-th datapoint, read from datastore \a ds */
-        virtual double getXErrorU(int i, JKQTPDatastore* ds) const;
+        virtual double getXErrorU(int i, const JKQTPDatastore* ds) const;
         /** \brief returns the lower x-error for the i-th datapoint, read from datastore \a ds */
-        virtual double getXErrorL(int i, JKQTPDatastore* ds) const;
+        virtual double getXErrorL(int i, const JKQTPDatastore *ds) const;
 
 };
 
@@ -277,9 +277,9 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPYGraphErrorData  {
         JKQTPErrorPlotstyle yErrorStyle;
 
         /** \brief returns the upper y-error for the i-th datapoint, read from datastore \a ds */
-        virtual double getYErrorU(int i, JKQTPDatastore* ds) const;
+        virtual double getYErrorU(int i, const JKQTPDatastore* ds) const;
         /** \brief returns the lower y-error for the i-th datapoint, read from datastore \a ds */
-        virtual double getYErrorL(int i, JKQTPDatastore* ds) const;
+        virtual double getYErrorL(int i, const JKQTPDatastore* ds) const;
 
 };
 
@@ -301,7 +301,7 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPXGraphErrors: public JKQTPXGraphErrorData, pub
 
     protected:
         /** \brief draws the error indicators */
-        virtual void plotErrorIndicators(JKQTPEnhancedPainter& painter, JKQTBasePlotter* parent, JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift=0, double yrelshift=0.0, const QVector<int> *dataorder=nullptr) const ;
+        virtual void plotErrorIndicators(JKQTPEnhancedPainter& painter, const JKQTBasePlotter* parent, const JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift=0, double yrelshift=0.0, const QVector<int> *dataorder=nullptr) const ;
 
 };
 
@@ -323,7 +323,7 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPYGraphErrors: public JKQTPYGraphErrorData, pub
 
     protected:
         /** \brief draws the error indicators */
-        virtual void plotErrorIndicators(JKQTPEnhancedPainter& painter, JKQTBasePlotter* parent, JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift=0, double yrelshift=0.0, const QVector<int> *dataorder=nullptr) const ;
+        virtual void plotErrorIndicators(JKQTPEnhancedPainter& painter, const JKQTBasePlotter* parent, const JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift=0, double yrelshift=0.0, const QVector<int> *dataorder=nullptr) const ;
 
 };
 
@@ -347,7 +347,7 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPXYGraphErrors: public JKQTPXGraphErrorData, pu
 
     protected:
         /** \brief draws the error indicators */
-        virtual void plotErrorIndicators(JKQTPEnhancedPainter& painter, JKQTBasePlotter* parent, JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift=0, double yrelshift=0.0, const QVector<int> *dataorder=nullptr) const ;
+        virtual void plotErrorIndicators(JKQTPEnhancedPainter& painter, const JKQTBasePlotter* parent, const JKQTPGraph* parentGraph, int xColumn, int yColumn, double xrelshift=0, double yrelshift=0.0, const QVector<int> *dataorder=nullptr) const ;
 
 };