# Example (JKQTPlotter): Different Types of Errorindicators {#JKQTPlotterErrorBarStyles} This project (see `./examples/simpletest_errorbarstyles/`) simply creates a JKQTPlotter widget (as a new window) and adds several curves show-casing different styles of error indicators. Data is initialized from two QVector objects. [JKQTPlotterBasicJKQTPDatastoreStatisticsGroupedStat]: @ref JKQTPlotterBasicJKQTPDatastoreStatisticsGroupedStat "1-Dimensional Group Statistics with JKQTPDatastore" [statisticslibrary]: @ref jkqtptools_math_statistics "JKQTPlotter Statistics Library" ***Note:*** This examples explains how to plot graphs with error indicators, when the data has already been calculated. The tutorial [JKQTPlotterBasicJKQTPDatastoreStatisticsGroupedStat] explains one way how to use the [statisticslibrary] in order to calculate the errors from data. The source code of the main application can be found in [`jkqtplotter_simpletest_errorbarstyles.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/simpletest_errorbarstyles/jkqtplotter_simpletest_errorbarstyles.cpp). First some data is added to the internal datastore (mostly, like explained in several other examples, like e.g. [Line Graph with Different Symbols and Line Styles](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/simpletest_symbols_and_styles)). The (in a loop) several graphs are added, each with a distinct style for its error indicators: ```.cpp // 3. now we make several plots with different error styles // for that we iterate over every style from the vector errorStyles // the array showXandYError indicates whether we want x- and y-error // for a style for all stywhere this is false, only y-error-indicators // are shown QVector errorStyles {JKQTPNoError, JKQTPErrorBars, JKQTPErrorSimpleBars, JKQTPErrorLines, JKQTPErrorPolygons, JKQTPErrorBoxes, JKQTPErrorEllipses, JKQTPErrorBarsPolygons, JKQTPErrorBarsLines, JKQTPErrorSimpleBarsLines, JKQTPErrorSimpleBarsPolygons }; QVector showXandYError { false , true , true , false , false , true , true , false , false , false , false }; for (int errorID=0; errorID Y; for (auto& xx: X) { Y<(errorID)*2.5; } // create a graph object JKQTPXYLineErrorGraph* graph=new JKQTPXYLineErrorGraph(&plot); // copy data into datastore and immediately set the yColumn graph->setXColumn(columnX); graph->setYColumn(ds->addCopiedColumn(Y, "y"+QString::number(errorID))); graph->setXErrorColumn(columnXError); graph->setYErrorColumn(columnYError); // set error style, for the y-axis graph->setYErrorStyle(errorStyles[errorID]); // no error indicators for the x-values graph->setXErrorStyle(JKQTPNoError); // ... unless: for some error styles we want error in both directions if (showXandYError[errorID]) { graph->setXErrorStyle(errorStyles[errorID]); graph->setDrawLine(false); } // make error indicator 30% transparent QColor c=graph->getErrorFillColor(); c.setAlphaF(0.3); graph->setErrorFillColor(c); // set error indicator line width graph->setErrorLineWidth(1); // set length of small bars at the end of error bars graph->setErrorBarCapSize(15); // set symbol (cross/X) + pen style (and color)dashed) graph->setSymbolType(JKQTPCross); graph->setLineStyle(Qt::DashLine); // set symbol size graph->setSymbolSize(5); // set width of symbol lines graph->setSymbolLineWidth(1); // set width of graph line graph->setLineWidth(1); // graph title is made from symbol+errorStylestyle, we use the LaTeX instruction \verb around the // result of JKQTPErrorPlotstyle2String(), because it contains underscores that would otherwise // lead to lower-case letter, which we don't want graph->setTitle("\\verb{"+JKQTPErrorPlotstyle2String(errorStyles[errorID])+"}"); // add the graph to the plot, so it is actually displayed plot.addGraph(graph); } ``` The error styles are set in these lines: ```.cpp // set error style, for the y-axis graph->setYErrorStyle(errorStyles[errorID]); // no error indicators for the x-values graph->setXErrorStyle(errorStyles[errorID]); ``` There are several variables that can be used to further style the error indicator, like: ```.cpp // make error indicator 30% transparent QColor c=graph->getErrorFillColor(); c.setAlphaF(0.3); graph->setErrorFillColor(c); // set error indicator line width graph->setErrorLineWidth(1); // set length of small bars at the end of error bars graph->setErrorBarCapSize(15); ``` There are more properties that you can find in the documentation of the mix-in classes `JKQTPXYGraphErrors`, `JKQTPXGraphErrors`, `JKQTPYGraphErrors`, `JKQTPGraphErrors`. In addition the plot key is moved outside the pot and the grid in the plot is switched off: ```.cpp // 6. change locaion of key (outside top-right) plot.getPlotter()->setKeyPosition(JKQTPKeyOutsideRightTop); // ... and switch off the grid plot.getXAxis()->setDrawGrid(false); plot.getXAxis()->setDrawMinorGrid(false); plot.getYAxis()->setDrawGrid(false); plot.getYAxis()->setDrawMinorGrid(false); ``` The result looks like this: ![jkqtplotter_simpletest_errorbarstyles](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_errorbarstyles.png) Error bars are implemented in the mixin-classes `JKQTPXYGraphErrors`, `JKQTPXGraphErrors` and `JKQTPYGraphErrors` that are all derived from `JKQTPGraphErrors`. With these it is simple to add error indicators to several different plot styles. Usually you can recognize these by looking at the class name, e.g. `JKQTPXYLineGraph` is a simple line+symbol graph, and `JKQTPXYLineErrorGraph` is the same with error indictaors (see above). There are also several other plots with error indicators: - `JKQTPBarVerticalErrorGraph` for barcharts with errors:
![](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_errorbarstyles_barcharts.png) - `JKQTPImpulsesVerticalGraph` for impulse/candle-stick charts with errors:
![](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_errorbarstyles_impulses.png) - `JKQTPFilledCurveXErrorGraph` for filled curves with errors:
![](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_errorbarstyles_filledcurves.png) .