QChart还有专门画极坐标的类QPolarChart，它的界面是一个圆盘。

#include <QApplication>
#include <QDebug>
#include <QtCharts/QScatterSeries>
#include <QtCharts/QLineSeries>
#include <QtCharts/QPolarChart>
#include <QtCharts/QValueAxis>
#include <QtCharts/QChartView>
#include "mainwindow.h"
//[1]
QT_CHARTS_USE_NAMESPACE

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //曲线
    QLineSeries *seriesLine = new QLineSeries();    
    seriesLine->setName("LinePolar");


    //图表
    QPolarChart *polarChart = new QPolarChart();
    polarChart->addSeries(seriesLine);
    polarChart->setTitle("First Polar Chart");

    //坐标轴
    QValueAxis *angleAxis = new QValueAxis();
    angleAxis->setTickCount(9);
    angleAxis->setLabelFormat("%d");
    //角度
    polarChart->addAxis(angleAxis, QPolarChart::PolarOrientationAngular);    

    QValueAxis *radiusAxis = new QValueAxis();
    radiusAxis->setTickCount(9);
    radiusAxis->setLabelFormat("%d");
    //半径
    polarChart->addAxis(radiusAxis, QPolarChart::PolarOrientationRadial);

    seriesLine->attachAxis(radiusAxis);
    seriesLine->attachAxis(angleAxis);

    radiusAxis->setRange(0, 360); //设置半径范围
    angleAxis->setRange(0, 360);    //设置角度范围

    for (int i = 0; i <= 360; i += 10)
        seriesLine->append(i, (i / 360.0) * 360);

    QChartView *polarChartView = new QChartView();
    polarChartView->setChart(polarChart);

    MainWindow w;
    w.SetWidget(polarChartView);
    w.show();

    return a.exec();
}

 setTickCount(int count)设置大刻度线的数目，默认是5，不能小于2。程序中设置的是9，但是数一下好像不对。setTickCount(4)换个4体验一下。对于半径，第4条线就是圆心，看不太出来。对于角度，第1条和第4条线会重合。

 QPolarChart自带了一些主题，跟手机一样可以换主题，默认主题就是上面的效果，换个Dark主题：

polarChart->setTheme(QChart::ChartThemeDark);     //设置主题 

还有蓝色，棕色等其他主题，具体主题如下：

主题名	描述
QChart::ChartThemeLight	The light theme, which is the default theme.
QChart::ChartThemeBlueCerulean	The cerulean blue theme.
QChart::ChartThemeDark	The dark theme.
QChart::ChartThemeBrownSand	The sand brown theme.
QChart::ChartThemeBlueNcs	The natural color system (NCS) blue theme.
QChart::ChartThemeHighContrast	The high contrast theme.
QChart::ChartThemeBlueIcy	The icy blue theme.
QChart::ChartThemeQt	The Qt theme.