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Version: 5.1

Radar chart

(quoted from Radar chart definition in Wikipedia)

A radar chart is a graphical method of displaying multivariate data in the form of a two-dimensional chart of three or more quantitative variables represented on axes starting from the same point. The relative position and angle of the axes is typically uninformative. It is equivalent to a parallel coordinates plot, with the axes arranged radially.

They are often useful for comparing the points of two or more different data sets.

Programmatically, you could use a radar chart as following:

// creates the chart    
RadarChart chart = new RadarChart();
// adds to DOM
component.add(chart);
...
// example for Elemental2
// gets the chart instance as DOM element
Element element = chart.getChartElement().as();
// adds to DOM
DomGlobal.document.body.appendChild(element);

By UIBinder (ONLY for GWT), you could use a radar chart as following:

<ui:UiBinder xmlns:ui="urn:ui:com.google.gwt.uibinder"
xmlns:g="urn:import:com.google.gwt.user.client.ui"
xmlns:c="urn:import:org.pepstock.charba.client.gwt.widgets">

<g:HTMLPanel width="100%">
....
<c:RadarChartWidget ui:field="chart"/>
...
</g:HTMLPanel>
</ui:UiBinder>

Dataset

The radar chart allows to define the data and a number of properties, used to display the data, by a radar dataset.

Every chart has got a method to create a typed dataset accordingly with the chart type. The dataset can be also created instantiating the constructor.

// creates the chart
RadarChart chart = new RadarChart();
// creates the dataset
RadarDataset dataset = chart.newDataset();
// sets the option
dataset.setBackgroundColor(HtmlColor.RED);
...
// creates the dataset
RadarDataset datasetNew = new RadarDataset();
// sets the option
datasetNew.setBackgroundColor(HtmlColor.RED);
...
// sets the datasets to the chart
chart.getData().setDatasets(dataset, datasetNew);

The following are the attributes that you can set:

NameTypeScriptableDescription
backgroundColorString - IsColor - Pattern - GradientYesThe fill color under the line.
borderCapStyleCapStyleYesCap style of the line. See MDN.
borderColorString - IsColor - GradientYesThe color of the line.
borderDashint[]YesLength and spacing of dashes. See MDN.
borderDashOffsetdoubleYesOffset for line dashes. See MDN.
borderJoinStyleJoinStyleYesLine joint style. See MDN.
borderWidthintYesThe width of the line in pixels.
clipboolean - double - Clip-How to clip relative to chart area. Positive value allows overflow, negative value clips that many pixels inside chart area.
drawActiveElementsOnTopbooleanYesDraw the active points of a dataset over the other points of the dataset.
fillString - int - boolean - IsFillYesHow to fill the area under the line. See Filling modes.
hoverBackgroundColorString - IsColor - Pattern - GradientYesThe fill color under the line, when hovered.
hoverBorderCapStyleCapStyleYesCap style of the line, when hovered. See MDN.
hoverBorderColorString - IsColor - GradientYesThe color of the line, when hovered.
hoverBorderDashint[]YesLength and spacing of dashes, when hovered. See MDN.
hoverBorderDashOffsetintYesOffset for line dashes, when hovered. See MDN.
hoverBorderJoinStyleJoinStyleYesLine joint style, when hovered. See MDN.
hoverBorderWidthintYesThe width of the line in pixels, when hovered.
labelString-The label for the dataset which appears in the legend and tooltips.
normalizedboolean-If true, you provide data with indices that are unique, sorted, and consistent across data sets and provide the normalized.
orderint-The drawing order of dataset. Also affects order for stacking, tooltip, and legend.
parsingboolean-If false, the data set parsing is disable. If parsing is disabled, data must be sorted and in the formats the associated chart type and scales use internally.
pointBackgroundColorString[] - IsColor[] - Gradient[]YesThe fill color for points.
pointBorderColorString[] - IsColor[] - Gradient[]YesThe border color for points.
pointBorderWidthint[]YesThe width of the point border in pixels.
pointHitRadiusdouble[]YesThe pixel size of the non-displayed point that reacts to mouse events.
pointHoverBackgroundColorString[] - IsColor[] - Gradient[]YesPoint background color when hovered.
pointHoverBorderColorString[] - IsColor[] - Gradient[]YesPoint border color when hovered.
pointHoverBorderWidthint[]YesBorder width of point when hovered.
pointHoverRadiusdouble[]YesThe radius of the point when hovered.
pointRadiusdouble[]YesThe radius of the point shape. If set to 0, the point is not rendered.
pointRotationdouble[]Yesthe rotation of the point in degrees.
pointStylePointStyle[] - Img[] - Canvas[]YesStyle of the point.
spanGapsboolean-If true, lines will be drawn between points with no or null data. If false, points with NaN data will create a break in the line.
tensiondouble-Bezier curve tension of the line. Set to 0 to draw straight lines.

General

The general options for a line dataset can control behaviors not related to styling or interactions and they are the following:

NameDefaultsDescription
clipUndefined.DOUBLEHow to clip relative to chart area.
drawActiveElementsOnToptrueDraw the active points of a dataset over the other points of the dataset.
labelnullThe label for the dataset which appears in the legend and tooltip.
normalizedfalseIf true, you provide data with indices that are unique, sorted, and consistent across data sets and provide the normalized.
order0The drawing order of dataset. Also affects order for stacking, tooltip, and legend.
parsingtrueIf false, the data set parsing is disable. If parsing is disabled, data must be sorted and in the formats the associated chart type and scales use internally.

Point styling

The style of each point of the dataset can be configured by the following properties:

NameDescription
pointBackgroundColorThe fill color for points.
pointBorderColorThe border color for points.
pointBorderWidthThe width of the point border in pixels.
pointHitRadiusThe pixel size of the non-displayed point that reacts to mouse events.
pointRadiusThe radius of the point shape.
pointRotationThe rotation of the point in degrees.
pointStyleStyle of the point.

All above options have got the fallback to the associated Point elements, retrievable by the following statements:

// from chart instance
Point point = chart.getOptions().getElements().getPoint();
// sets options for all line datasets of the chart
point.setRadius(6);
...
// from defaults
Point defaultPoint = Defaults.get().getGlobal().getElements().getPoint();
// sets options for all line datasets of all charts
defaultPoint.setRadius(6);

Line styling

The style of each line of the dataset can be configured by the following properties:

NameDescription
backgroundColorThe fill color under the line.
borderCapStyleCap style of the line.
borderColorThe color of the line.
borderDashLength and spacing of dashes.
borderDashOffsetOffset for line dashes.
borderJoinStyleLine joint style.
borderWidthThe width of the line in pixels.
fillHow to fill the area under the line.
tensionBezier curve tension of the line.

All above options have got the fallback to the associated Line elements, retrievable by the following statements:

// from chart instance
Line line = chart.getOptions().getElements().getLine();
// sets options for all line datasets of the chart
line.setBorderWidth(6);
...
// from defaults
Line defaultLine = Defaults.get().getGlobal().getElements().getLine();
// sets options for all line datasets of all charts
defaultLine.setBorderWidth(6);

Point interactions

The interaction with each point can be controlled with the following properties:

NameDescription
pointHoverBackgroundColorPoint background color when hovered.
pointHoverBorderColorPoint border color when hovered.
pointHoverBorderWidthBorder width of point when hovered.
pointHoverRadiusThe radius of the point when hovered.

All above options have got the fallback to the associated Point elements, retrievable by the following statements:

// from chart instance
Point point = chart.getOptions().getElements().getPoint();
// sets options for all line datasets of the chart
point.setRadius(6);
...
// from defaults
Point defaultPoint = Defaults.get().getGlobal().getElements().getPoint();
// sets options for all line datasets of all charts
defaultPoint.setRadius(6);

Line interactions

The interaction with each line can be controlled with the following properties:

NameDescription
hoverBackgroundColorThe fill color/pattern under the line, when hovered.
hoverBorderCapStyleCap style of the line, when hovered.
hoverBorderColorThe color of the line, when hovered.
hoverBorderDashLength and spacing of dashes, when hovered.
hoverBorderDashOffsetOffset for line dashes, when hovered.
hoverBorderJoinStyleLine joint style, when hovered.
hoverBorderWidthThe width of the line in pixels, when hovered.

All above options have got the fallback to the associated Line elements, retrievable by the following statements:

// from chart instance
Line line = chart.getOptions().getElements().getLine();
// sets options for all line datasets of the chart
line.setBorderWidth(6);
...
// from defaults
Line defaultLine = Defaults.get().getGlobal().getElements().getLine();
// sets options for all line datasets of all charts
defaultLine.setBorderWidth(6);

Scriptable

Scriptable options at dataset level accept a callback which is called for each of the underlying data values. See more details in Configuring charts section.

// creates chart
RadarChart chart = new RadarChart();
// creates dataset
RadarDataset dataset = chart.newDataset();
// sets the option by a callback
dataset.setBackgroundColor(new ColorCallback<DatasetContext>(){

@Override
public IsColor invoke(DatasetContext context){
// logic
return color;
}
});

The following options can be set by a callback:

NameCallbackReturned types
backgroundColorColorCallback<DatasetContext>String - IsColor - Pattern - Gradient
borderCapStyleCapStyleCallback<DatasetContext>CapStyle
borderColorColorCallback<DatasetContext>String - IsColor - Gradient
borderDashBorderDashCallback<DatasetContext>List<Integer>
borderDashOffsetBorderDashOffsetCallback<DatasetContext>double
borderJoinStyleJoinStyleCallback<DatasetContext>JoinStyle
borderWidthWidthCallback<DatasetContext>int
cubicInterpolationModeCubicInterpolationModeCallbackCubicInterpolationMode
drawActiveElementsOnTopDrawActiveElementsOnTopCallbackboolean
fillFillCallbackString - int - boolean - IsFill
hoverBackgroundColorColorCallback<DatasetContext>String - IsColor - Pattern - Gradient
hoverBorderCapStyleCapStyleCallback<DatasetContext>CapStyle
hoverBorderColorColorCallback<DatasetContext>String - IsColor - Gradient
hoverBorderDashBorderDashCallback<DatasetContext>List<Integer>
hoverBorderDashOffsetBorderDashOffsetCallback<DatasetContext>int
hoverBorderJoinStyleJoinStyleCallback<DatasetContext>JoinStyle
hoverBorderWidthWidthCallback<DatasetContext>int
pointBackgroundColorColorCallback<DatasetContext>String - IsColor - Gradient
pointBorderColorColorCallback<DatasetContext>String - IsColor - Gradient
pointBorderWidthWidthCallback<DatasetContext>int
pointHitRadiusRadiusCallback<DatasetContext>double
pointHoverBackgroundColorColorCallback<DatasetContext>String - IsColor - Gradient
pointHoverBorderColorColorCallback<DatasetContext>String - IsColor - Gradient
pointHoverBorderWidthWidthCallback<DatasetContext>int
pointHoverRadiusRadiusCallback<DatasetContext>double
pointRadiusRadiusCallback<DatasetContext>double
pointRotationRotationCallback<DatasetContext>double
pointStylePointStyleCallback<DatasetContext>PointStyle - Img - Canvas

Data structure

The data of a dataset for a radar chart is specified as a an array of numbers. Each point in the data array corresponds to the label at the same index on the x axis.

// sets data as an array of doubles
dataset.setData(1,2,3,4,6);

// sets data as a list of double
List<Double> list = new LinkedList<>();
list.add(1);
list.add(2);
list.add(3);
dataset.setData(list);

To provide context of what each point means, we include an array of strings that show around each point in the chart.

...
chart.getData().setLabels("label1", "label2");
...

Options

The radar chart defines specific options implementation to be configured. These options are merged with the global chart configuration options to form the options passed to the chart.

// creates chart
RadarChart chart = new RadarChart();
// gets the chart options
RadarOptions options = chart.getOptions();
// sets options
options.setResponsive(true);
options.setSpanGaps(true);

These are the options specific to radar charts:

NameTypeDefaultDescription
spanGapsbooleanfalseIf true, lines will be drawn between points with no or null data. If false, points with NaN data will create a break in the line.