mirror of
https://github.com/jkriege2/JKQtPlotter.git
synced 2024-11-15 18:15:52 +08:00
107 lines
5.9 KiB
Markdown
107 lines
5.9 KiB
Markdown
# Example (JKQTPlotter): Line Graph with Logarithmic y-axis {#JKQTPlotterLogAxes}
|
|
This project (see `./examples/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 [`logaxes.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/logaxes/logaxes.cpp). Mainly several graphs are generated in a loop and then different line styles are applied to the graphs (set by ``graph->setLineStyle()`). The colors are set automtically from an internal default palette. The main loop looks like this:
|
|
|
|
```.cpp
|
|
QVector<Qt::PenStyle> pens {Qt::SolidLine, Qt::DashLine, Qt::DotLine, Qt::DashDotLine, Qt::DashDotDotLine };
|
|
for (int id=0; id<D.size(); id++) {
|
|
// generate some plot data
|
|
QVector<double> 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->setXColumn(columnX);
|
|
graph->setYColumn(ds->addCopiedColumn(Y, "y"+QString::number(id)));
|
|
|
|
// don't use symbols
|
|
graph->setSymbolType(JKQTPNoSymbol);
|
|
// use one of different pens
|
|
graph->setLineStyle(pens[id%pens.size()]);
|
|
// set width of graph line
|
|
graph->setLineWidth(1.5);
|
|
|
|
// graph title is made from symbol+penstyle
|
|
graph->setTitle(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:
|
|
```.cpp
|
|
// 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, QColor("black")));
|
|
```
|
|
The difference between not using and using `$...$` for the equation can be seen here:
|
|
- no $-math-mode: 
|
|
- using $-math-mode: 
|
|
|
|
Finally the y-axis is switched to logarithmic scaling and the axis labels are set:
|
|
```.cpp
|
|
// 5. set y-axis to logarithmic (x-axis would be analogous, but using `plot.getXAxis()`)
|
|
plot.getYAxis()->setLogAxis(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.getYAxis()->setMinorTicks(9);
|
|
// the minor grid is not shown by default. You can switch it on:
|
|
plot.getYAxis()->setDrawMinorGrid(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.getYAxis()->setLabelType(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.getYAxis()->setLabelDigits(0);
|
|
// minor tick labels are usually not displayed, but you can switch them on, using
|
|
//plot.getYAxis()->setMinorTickLabelsEnabled(true);
|
|
// the axis font sizes can be set with:
|
|
plot.getYAxis()->setTickLabelFontSize(10); // axis tick labels
|
|
plot.getYAxis()->setMinorTickLabelFontSize(7); // minor axis tick labels
|
|
plot.getYAxis()->setLabelFontSize(14); // axis label size
|
|
plot.getXAxis()->setTickLabelFontSize(10); // axis tick labels
|
|
plot.getXAxis()->setMinorTickLabelFontSize(7); // minor axis tick labels
|
|
plot.getXAxis()->setLabelFontSize(14); // axis label size
|
|
// ... and finally set axis labels (using LaTeX notation and $...$ to improve rendering)
|
|
plot.getYAxis()->setAxisLabel("Amplitude $A/A_{stat}$");
|
|
plot.getXAxis()->setAxisLabel("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:
|
|
|
|
|
|
|
|
Without the logarithmic scaling we would have:
|
|
|
|
|
|
|
|
Switching the minor grid off results in a plot like this:
|
|
|
|
|
|
|
|
These examples show the results for different typical values for `setMinorTicks()`:
|
|
|
|
|
|
|
|
These examples show the results for different typical values for `setLabelType()`:
|
|
|
|
|
|
|
|
|
|
|