使用 qcustomplot
创建绘图后,如何根据现有X值检索Y值,然后在这些位置绘制点?
我的尝试如下:
Create plot:
此函数创建绘图,在x轴上添加一些数据(日期),在y轴上添加一些值:
void Qt_PlotTest::createPlot(){
QCustomPlot* customPlot = ui.widget;
customPlot->setLocale(QLocale(QLocale::English, QLocale::UnitedKingdom));
//Set some data:
double now = QDateTime::currentDateTime().toTime_t();
QVector<double> yData, xData;
for (int i = 0; i < 100; i++){
xData.push_back(now + i*24.0 * 3600.0);
yData.push_back(pow(double(i), 2) + 550.0*sin(double(i)/4.0));
}
// create graph and assign data to it:
customPlot->addGraph();
customPlot->graph(0)->setData(xData, yData);
//Fix axes:
//Set date axis:
QSharedPointer<QCPAxisTickerDateTime> dateTicker(new QCPAxisTickerDateTime);
dateTicker->setDateTimeFormat("d. MMMM\nyyyy");
customPlot->xAxis->setTicker(dateTicker);
customPlot->xAxis->setLabel("Time");
customPlot->yAxis->setLabel("Value");
customPlot->rescaleAxes();
customPlot->replot();
//Set interations:
customPlot->setInteraction(QCP::iRangeDrag, true);
customPlot->setInteraction(QCP::iRangeZoom, true);
}
结果如下:
Set scatter points:
此函数应基于x值在正确的x / y位置绘制几个散点 . (我需要从现有的图中读取相应的Y值) .
void Qt_PlotTest::setScatterPoints(){
QCustomPlot* customPlot = ui.widget;
//The locations where scatter points should be plotted:
QDate qd1(2018, 03, 26), qd2(2018, 03, 30), qd3(2018, 05, 11), qd4(2018, 06, 15);
QVector<double> dates = { (double)QDateTime(qd1).toTime_t(), (double)QDateTime(qd2).toTime_t(), (double)QDateTime(qd3).toTime_t(), (double)QDateTime(qd4).toTime_t() };
//Use tracer to find data at these dates:
QVector<double> values;
QCPItemTracer *tracer = new QCPItemTracer(customPlot);
tracer->setGraph(customPlot->graph(0));
tracer->setInterpolating(true);
for (int i = 0; i < 4; i++){
tracer->setGraphKey(dates[i]);
values.push_back(tracer->position->coords().y());
}
//Plot points at these locations:
QCPGraph* dwPoints = new QCPGraph(customPlot->xAxis, customPlot->yAxis);
dwPoints->setAdaptiveSampling(false);
dwPoints->setLineStyle(QCPGraph::lsNone);
dwPoints->setScatterStyle(QCPScatterStyle::ssCircle);
dwPoints->setPen(QPen(QBrush(Qt::red), 2));
dwPoints->addData(dates, values);
customPlot->replot();
}
结果如下:
所以显然 QCPItemTracer
并不想要 . )
是 QCPItemTracer
我想用什么来实现我想要的?我还看到一些使用 QCPDataMap
的例子来找到基于X值的Y值 . 但据我了解, QCPDataMap
,已不再是 qcustomplot
.
1 回答
我解决了自己的问题:
我不得不调用
tracer->updatePosition()
来实际获取放置跟踪器的坐标系中的坐标 .我不想要的轴实际上是最终示踪剂位置处的示踪剂的可视化 . 我只需要调用
tracer->setVisibile(false)
来隐藏它 .所以在void
Qt_PlotTest::setScatterPoints
我有这个:Result: