- Qt 6.8
- Qt Charts
- Using Polar Charts with QML
- Qt Charts | Commercial or GPLv3

# Using Polar Charts with QML

Note: This is part of the Charts with QML Gallery example.

We begin with a chart that has a spline series and a scatter series with random data. Both series use the same axes.

     PolarChartView {
         title: "Two Series, Common Axes"
         anchors.fill: parent
         legend.visible: false
         antialiasing: true

         ValueAxis {
             id: axisAngular
             min: 0
             max: 20
             tickCount: 9
         }

         ValueAxis {
             id: axisRadial
             min: -0.5
             max: 1.5
         }

         SplineSeries {
             id: series1
             axisAngular: axisAngular
             axisRadial: axisRadial
             pointsVisible: true
         }

         ScatterSeries {
             id: series2
             axisAngular: axisAngular
             axisRadial: axisRadial
             markerSize: 10
         }

         // Add data dynamically to the series
         Component.onCompleted: {
             for (var i = 0; i <= 20; i++) {
                 series1.append(i, Math.random());
                 series2.append(i, Math.random());
             }
         }
     }

The next chart shows some accurate historical data for which we need to use a DateTimeAxis and a AreaSeries.

     PolarChartView {
         id: root
         title: "Historical Area Chart"
         anchors.fill: parent
         legend.visible: false
         antialiasing: true

         DateTimeAxis {
             id: axis1
             format: "yyyy MMM"
             tickCount: 13
         }
         ValueAxis {
             id: axis2
         }
         LineSeries {
             id: lowerLine
             axisAngular: axis1
             axisRadial: axis2

             // Please note that month in JavaScript months are zero based, so 2 means March
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1950, 0, 1)); y: 15 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1962, 4, 1)); y: 35 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1970, 0, 1)); y: 50 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1978, 2, 1)); y: 75 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1987, 11, 1)); y: 102 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1992, 1, 1)); y: 132 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1998, 7, 1)); y: 100 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(2002, 4, 1)); y: 120 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(2012, 8, 1)); y: 140 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(2013, 5, 1)); y: 150 }
         }
         LineSeries {
             id: upperLine
             axisAngular: axis1
             axisRadial: axis2

             // Please note that month in JavaScript months are zero based, so 2 means March
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1950, 0, 1)); y: 30 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1962, 4, 1)); y: 55 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1970, 0, 1)); y: 80 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1978, 2, 1)); y: 105 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1987, 11, 1)); y: 125 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1992, 1, 1)); y: 160 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(1998, 7, 1)); y: 140 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(2002, 4, 1)); y: 140 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(2012, 8, 1)); y: 170 }
             XYPoint { x: root.toMsecsSinceEpoch(new Date(2013, 5, 1)); y: 200 }
         }
         AreaSeries {
             axisAngular: axis1
             axisRadial: axis2
             lowerSeries: lowerLine
             upperSeries: upperLine
         }

         // DateTimeAxis is based on QDateTimes so we must convert our JavaScript dates to
         // milliseconds since epoch to make them match the DateTimeAxis values
         function toMsecsSinceEpoch(date) {
             var msecs = date.getTime();
             return msecs;
         }
     }

The next chart uses a CategoryAxis to make the data easier to understand.

     PolarChartView {
         title: "Numerical Data for Dummies"
         anchors.fill: parent
         legend.visible: false
         antialiasing: true

         LineSeries {
             axisRadial: CategoryAxis {
                 min: 0
                 max: 30
                 CategoryRange {
                     label: "critical"
                     endValue: 2
                 }
                 CategoryRange {
                     label: "low"
                     endValue: 7
                 }
                 CategoryRange {
                     label: "normal"
                     endValue: 12
                 }
                 CategoryRange {
                     label: "high"
                     endValue: 18
                 }
                 CategoryRange {
                     label: "extremely high"
                     endValue: 30
                 }
             }

             axisAngular: ValueAxis {
                 tickCount: 13
             }

             XYPoint { x: 0; y: 4.3 }
             XYPoint { x: 1; y: 4.1 }
             XYPoint { x: 2; y: 4.7 }
             XYPoint { x: 3; y: 3.9 }
             XYPoint { x: 4; y: 5.2 }
             XYPoint { x: 5; y: 5.3 }
             XYPoint { x: 6; y: 6.1 }
             XYPoint { x: 7; y: 7.7 }
             XYPoint { x: 8; y: 12.9 }
             XYPoint { x: 9; y: 19.2 }
         }
     }