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171 lines
7.5 KiB
Markdown
171 lines
7.5 KiB
Markdown
[Back to JKQTPlotter main page](https://github.com/jkriege2/JKQtPlotter/)
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# JKQtPlotter
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## Date/Time Axes
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### Date Axis
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This project (see `./test/simpletest_dateaxes/`) simply creates a JKQtPlotter widget (as a new window) with the X-axis showing time or date(-time) values, formated as such.
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The source code of the main application can be found in [`jkqtplotter_simpletest_dateaxes.cpp´]((https://github.com/jkriege2/JKQtPlotter/blob/master/test/simpletest_dateaxes/jkqtplotter_simpletest_dateaxes.cpp).
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First some data is parsed from a CSV-file (added as ressource to the example). Note that the Time/date or Date+Time data is internally stored as milliseconds since epoc (Jan 1st 1970, 00:00:00), therefore data has to be converted accordingly before beeing added to the graph.
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```c++
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QVector<double> date;
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QVector<double> temperature, temperature_min, temperature_max;
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// parse a textfile with comments on the first line and the
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// semicolon separated data. The first column is a date and time
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// the second to fourth columns contain a floating-point number
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// with temperature average, min and max
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QFile file(":/weatherdata_gelsenkirchen.csv");
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file.open(QFile::ReadOnly|QFile::Text);
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file.readLine(); // eat comment
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while (!file.atEnd()) {
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QString line=file.readLine();
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QTextStream in(&line);
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QStringList items=line.split(";");
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// date/time values are stored as doubles representing the corresponding number of milliseconds sind epoch
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date<<QDateTime::fromString(items[0], Qt::ISODate).toUTC().toMSecsSinceEpoch();
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// store Heidelbergs daily temperature
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temperature<<items[1].toDouble();
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temperature_min<<items[2].toDouble();
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temperature_max<<items[3].toDouble();
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}
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```
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The parsed data looks like this:
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```
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ISO-Date+Time;Temp_mean[degC];Temp_min[degC];Temp_max[degC]; data from http://wetter.mpg-ge.de/NOAA/NOAA-2018.txt and http://wetter.mpg-ge.de/NOAA/NOAA-2017.txt
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2017-01-15T12:00; 1.2; -1.2; 3.7
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2017-02-15T12:00; 5.6; 3.2; 8.1
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2017-03-15T12:00; 9.6; 6.2; 13.5
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...
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```
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Then two graphs are added. One of type `JKQTPfilledVerticalRangeGraph` plots the range of min+max temperature for each month:
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```c++
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// 3. add a plot for the data mean line (graphTemperature) and range (graphTemperatureRange)
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JKQTPfilledVerticalRangeGraph* graphTemperatureRange=new JKQTPfilledVerticalRangeGraph(&plot);
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// 4. copy data into datastore and immediately set the yColumn
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size_t colDate=ds->addCopiedColumn(date, "date");
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graphTemperatureRange->set_xColumn(colDate);
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graphTemperatureRange->set_yColumn(ds->addCopiedColumn(temperature_min, "temperature_min"));
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graphTemperatureRange->set_yColumn2(ds->addCopiedColumn(temperature_max, "temperature_max"));
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// 5. min/max range data
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// graph fill color is a lighter shade of the average graph
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graphTemperatureRange->set_fillColor(graphTemperature->get_color().lighter());
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// don't draw lines of the data
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graphTemperatureRange->set_drawLine(false);
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// plot label in key
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graphTemperatureRange->set_title("Min/Max Temperature");
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// add the graph to the plot, so it is actually displayed
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plot.addGraph(graphTemperatureRange);
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```
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On top of that plot, a second plot is added, which draws the average temperatures of each month as a line:
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```c++
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// 3. add a plot for the data mean line (graphTemperature) and range (graphTemperatureRange)
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JKQTPxyLineErrorGraph* graphTemperature=new JKQTPxyLineErrorGraph(&plot);
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// 4. copy data into datastore and immediately set the yColumn
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size_t colDate=ds->addCopiedColumn(date, "date");
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graphTemperature->set_xColumn(colDate);
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graphTemperature->set_yColumn(ds->addCopiedColumn(temperature, "temperature"));
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// 5. min/max range data
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// .... see above
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// 6. average data
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// don't use symbols
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graphTemperature->set_symbol(JKQTPnoSymbol);
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// set the line width
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graphTemperature->set_lineWidth(1);
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// draw small symbols
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graphTemperature->set_symbolSize(6);
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// graph title
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graphTemperature->set_title("Average Temperature");
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// add the graph to the plot, so it is actually displayed
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plot.addGraph(graphTemperature);
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```
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Finally the x-axis is formatted to display dates (see [Qt-Documentation of `QDateTime::toString()´]((http://doc.qt.io/qt-5/qdatetime.html#toString) for details on the formating strings):
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```c++
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// 7. format the plot
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// set the title above the plot, use LaTeX instructions to make text bold
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plot.get_plotter()->set_plotLabel("\\textbf{Weather in Gelsenkirchen, 2017-2018}");
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// set x-axis date-time-axis
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plot.getXAxis()->set_labelType(JKQTPCALTdatetime);
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plot.getXAxis()->set_axisLabel("Date");
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// set format string for date axis (e.g. Jan '18), see Documentation of QDateTime::toString()
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plot.getXAxis()->set_tickDateTimeFormat("MMM ''yy");
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// set y-axis temperature axis
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plot.getYAxis()->set_axisLabel("Average Daily Temperature [{\\degree}C]");
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```
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The result looks like this:
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### Time Axis
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A second variant (see the example CPP-file) displays data with a time-axis:
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For that example data-pasring is a bit different, because the file only contains times and no dates:
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```c++
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// 2. now we create data vectors with data parsed from a CSV-file
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QVector<double> time;
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QVector<double> temperature;
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// parse a textfile with comments on the first line and the
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// semicolon separated data. The first column is a time
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// the second contain a floating-point number with temperatures
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QFile file(":/weatherdata_heidelberg_2018-10-14.csv");
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file.open(QFile::ReadOnly|QFile::Text);
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file.readLine(); // eat comment
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while (!file.atEnd()) {
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QString line=file.readLine();
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QTextStream in(&line);
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QStringList items=line.split(";");
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// date/time values are stored as doubles representing the corresponding
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// number of milliseconds sind epoch. Since the data is time only, we have to use an arbitrary
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// date as basis
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time<<QDateTime::fromString("1970-01-01T"+items[0], Qt::ISODate).toUTC().toMSecsSinceEpoch();
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// store Heidelbergs daily temperature
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temperature<<items[1].toDouble();
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}
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```
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The parsed data looks like this:
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```
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Time; Temperature [degC]
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00:00:00; 24.2
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00:10:00; 24.2
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00:20:00; 24.1
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00:30:00; 24.1
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...
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```
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Axis formating for this example is done like this:
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```c++
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// 7. format the plot
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// set the title above the plot, use LaTeX instructions to make text bold
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plot.get_plotter()->set_plotLabel("\\textbf{Weather in Heidelberg, 14^{th} Oct 2018}");
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// set x-axis date-time-axis
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plot.getXAxis()->set_labelType(JKQTPCALTtime);
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plot.getXAxis()->set_axisLabel("Time of Day");
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// set format string for time axis with 24-hour and minute only,
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// see QDateTime::toString() documentation for details on format strings
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plot.getXAxis()->set_tickTimeFormat("HH:mm");
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// set y-axis temperature axis
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plot.getYAxis()->set_axisLabel("Temperature [{\\degree}C]");
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```
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[Back to JKQTPlotter main page](https://github.com/jkriege2/JKQtPlotter/) |