[Back to JKQTPlotter main page](https://github.com/jkriege2/JKQtPlotter/) # JKQtPlotter ## Line Graph with Logarithmic y-axis This project (see `./test/simpletest_logaxes/`) simply creates a JKQtPlotter widget (as a new window) and several line-graphs of different resonance curves. The source code of the main application can be found in [`jkqtplotter_simpletest_logaxes.cpp´]((https://github.com/jkriege2/JKQtPlotter/blob/master/test/simpletest_logaxes/jkqtplotter_simpletest_logaxes.cpp). Mainly several graphs are generated in a loop and then different line styles are applied to the graphs (set by ``graph->set_style()`). The colors are set automtically from an internal default palette. The main loop looks like this: ```c++ QVector pens {Qt::SolidLine, Qt::DashLine, Qt::DotLine, Qt::DashDotLine, Qt::DashDotDotLine }; for (int id=0; id Y; for (auto& xx: X) { Y<<1.0/sqrt(sqr(1-sqr(xx))+sqr(2*xx*D[id])); } JKQTPxyLineGraph* graph=new JKQTPxyLineGraph(&plot); // copy data into datastore and immediately set the yColumn graph->set_xColumn(columnX); graph->set_yColumn(ds->addCopiedColumn(Y, "y"+QString::number(id))); // don't use symbols graph->set_symbol(JKQTPnoSymbol); // use one of different pens graph->set_style(pens[id%pens.size()]); // set width of graph line graph->set_lineWidth(1.5); // graph title is made from symbol+penstyle graph->set_title(QString("D=\\delta/\\omega_0=%1").arg(D[id])); // add the graph to the plot, so it is actually displayed plot.addGraph(graph); } ``` Then a `JKQTPgeoText` is added to the graph, which shows the function plotted in the plot: ```c++ // 4. Also we add a text-element in the plot to show the plotted function // This element (JKQTPgeoText) is taken from the set of geometric elements // and is simply parametrized by a position (1.25/10) and the text to display. // In addition you can also set the font size (here to 15) // Use '$...$' around the actual math string to ensure rendering with a math font // (the internal renderer uses XITS fonts by default, which are free and auto-distributed // and loaded in the library). If you don't use the math-mode modifiers, the default // font of the other rendering text is used, which might not be suitable for // high-quality math rendering. plot.addGraph(new JKQTPgeoText(&plot, 1.25, 10, "$\\frac{A}{A_{stat}}=\\frac{1}{\\sqrt{\\left(1-\\eta^2\\right)^2+\\left(2{\\eta}D\\right)^2}}$", 15)); ``` The difference between not using and using `$...$` for the equation can be seen here: - no $-math-mode: ![](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_logaxes_lowqmathrendering.png) - using $-math-mode: ![](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_logaxes_highqmathrendering.png) Finally the y-axis is switched to logarithmic scaling and the axis labels are set: ```c++ // 5. set y-axis to logarithmic (x-axis would be analogous, but using `plot.get_xAxis()`) plot.get_yAxis()->set_logAxis(true); // now we set the number of label ticks to 9 (you give the count if minor between two majors, // so if you want ticks for 1,2,3,...,10,20,30,...,100... you need to use 9: plot.get_yAxis()->set_minorTicks(9); // the minor grid is not shown by default. You can switch it on: plot.get_yAxis()->set_drawMinorGrid(true); // usually axis ticks are shown as numbers 0.01, 0.1, 1, 10, ... You can also force the scientific // power-of-10 notation, using: plot.get_yAxis()->set_labelType(JKQTPCALTexponent); // the number of digits in JKQTPCALTexponent determines which labels are drawn in standard-notation, // as compared to power-notation (e.g. if set to 1, the labels 0.1=10^{-1}, 1, 10 are shown in // standard notation, the rest in power-notation. This tweak improves readability) plot.get_yAxis()->set_labelDigits(0); // minor tick labels are usually not displayed, but you can switch them on, using //plot.get_yAxis()->set_minorTickLabelsEnabled(true); // the axis font sizes can be set with: plot.get_yAxis()->set_tickLabelFontSize(10); // axis tick labels plot.get_yAxis()->set_minorTickLabelFontSize(7); // minor axis tick labels plot.get_yAxis()->set_labelFontSize(14); // axis label size plot.get_xAxis()->set_tickLabelFontSize(10); // axis tick labels plot.get_xAxis()->set_minorTickLabelFontSize(7); // minor axis tick labels plot.get_xAxis()->set_labelFontSize(14); // axis label size // ... and finally set axis labels (using LaTeX notation and $...$ to improve rendering) plot.get_yAxis()->set_axisLabel("Amplitude $A/A_{stat}$"); plot.get_xAxis()->set_axisLabel("relative driving frequency $\\eta=\\omega/\\omega_0$"); ``` As an alternative `JKQTPCALTexponentCharacter` does not use the power-of-10 notation, but uses the usual unit-characters, e.g. 0.001=1m, 0.000001=1µ, 10000=10k, ... The result looks like this: ![jkqtplotter_simpletest_logaxes](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_logaxes.png) Without the logarithmic scaling we would have: ![jkqtplotter_simpletest_logaxes_nolog](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_logaxes_nolog.png) Switching the minor grid off results in a plot like this: ![jkqtplotter_simpletest_logaxes_nominorgrid](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_logaxes_nominorgrid.png) These examples show the results for different typical values for `set_minorTicks()`: ![logaxis_set_minorticks](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/logaxis_set_minorticks.png) These examples show the results for different typical values for `set_labelType()`: ![logaxis_set_labelType](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/logaxis_set_labelType.png) [Back to JKQTPlotter main page](https://github.com/jkriege2/JKQtPlotter/)