示例qcustomplot多条曲线多个Y轴

在QCustomPlot中，可以使用addGraph()函数添加多条曲线，使用QCPAxisRect类创建多个Y轴。

以下是一个示例代码：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "qcustomplot.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    //创建QCustomPlot对象
    QCustomPlot *customPlot = new QCustomPlot(this);
    customPlot->setGeometry(50, 50, 600, 400);

    //添加多个Y轴
    QCPAxisRect *axisRect1 = new QCPAxisRect(customPlot);
    customPlot->plotLayout()->addElement(0, 0, axisRect1);
    axisRect1->setupFullAxesBox(true);
    axisRect1->axis(QCPAxis::atLeft)->setLabel("y1");
    QCPAxisRect *axisRect2 = new QCPAxisRect(customPlot);
    customPlot->plotLayout()->addElement(0, 1, axisRect2);
    axisRect2->setupFullAxesBox(true);
    axisRect2->axis(QCPAxis::atLeft)->setLabel("y2");

    //添加曲线
    QVector<double> x(101), y0(101), y1(101), y2(101), y3(101);
    for (int i=0; i<101; i++)
    {
        x[i] = i/50.0-1;
        y0[i] = qExp(-x[i]*x[i]*2);
        y1[i] = qSin(x[i]*3);
        y2[i] = qCos(x[i]*3);
        y3[i] = qTan(x[i]*3);
    }

    QCPGraph *graph0 = customPlot->addGraph(axisRect1->axis(QCPAxis::atBottom), axisRect1->axis(QCPAxis::atLeft));
    graph0->setData(x, y0);
    graph0->setPen(QPen(Qt::blue));
    QCPGraph *graph1 = customPlot->addGraph(axisRect2->axis(QCPAxis::atBottom), axisRect2->axis(QCPAxis::atLeft));
    graph1->setData(x, y1);
    graph1->setPen(QPen(Qt::red));
    QCPGraph *graph2 = customPlot->addGraph(axisRect2->axis(QCPAxis::atBottom), axisRect2->axis(QCPAxis::atLeft, 1));
    graph2->setData(x, y2);
    graph2->setPen(QPen(Qt::green));
    QCPGraph *graph3 = customPlot->addGraph(axisRect2->axis(QCPAxis::atBottom), axisRect2->axis(QCPAxis::atLeft, 2));
    graph3->setData(x, y3);
    graph3->setPen(QPen(Qt::black));

    //设置坐标轴范围
    axisRect1->axis(QCPAxis::atBottom)->setRange(-1, 1);
    axisRect1->axis(QCPAxis::atLeft)->setRange(0, 1);
    axisRect2->axis(QCPAxis::atBottom)->setRange(-1, 1);
    axisRect2->axis(QCPAxis::atLeft)->setRange(-1, 1);
    axisRect2->axis(QCPAxis::atLeft, 1)->setRange(-1, 1);
    axisRect2->axis(QCPAxis::atLeft, 2)->setRange(-10, 10);

    //添加图例
    customPlot->legend->setVisible(true);
    customPlot->legend->setFont(QFont("Helvetica", 9));
    customPlot->legend->setBrush(QBrush(QColor(255,255,255,230)));

    //显示图形
    customPlot->replot();
}

MainWindow::~MainWindow()
{
    delete ui;
}

该代码会在窗口中显示一个包含多条曲线和多个Y轴的QCustomPlot对象，每个Y轴对应一条曲线。其中，QCPAxisRect类用于创建多个Y轴，addGraph()函数用于添加多条曲线，setData()函数用于设置曲线的数据，setPen()函数用于设置曲线颜色，axis()函数用于获取坐标轴对象，setRange()函数用于设置坐标轴范围，legend类用于添加图例。