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Radar Chart (Radar)

This chapter explains how Radar charts work in EasyChart: where dimension labels come from, how value ranges are calculated, and how data point order is interpreted, mapped to Inspector fields.

1. Use cases

  • Multi-dimensional metric comparison
  • Ability/attribute radar

2. Minimum viable setup (checklist)

  1. ChartProfile.coordinateSystem = Polar2D
  2. Series

    3. - Add 1 Serie - Serie.type = Radar - Serie.seriesData is recommended to have at least 3 points (with <= 2 dimensions, runtime will not draw / hover won't work)

  3. PolarAxes (recommended)

    4. - polarAxes.angleAxis.labels: dimension names - polarAxes.radiusAxis: value range (auto/manual)

3. Inspector fields

  • ChartProfile / Coordinate System

    • - coordinateSystem = Polar2D

  • PolarAxes (recommended for configuring Radar axes)

    • - polarAxes.angleAxis.labels: dimension labels - polarAxes.radiusAxis.autoRangeMin/autoRangeMax/minValue/maxValue/autoRangeRounding/labelFormat/...

  • Series

    • - series[i].type = Radar - series[i].settings: actual type is RadarSettings - radar: layout (startAngleDeg / clockwise / innerRadius / outerRadius / plot / background) - stroke: polyline style - area: area fill - point: point style (point visibility also affects hover pick radius) - series[i].labelSettings: data point labels (can show dimension name and value)

4. SeriesData field interpretation (runtime behavior)

Key point for Radar: dimension order is defined by the index of items in the seriesData list.

  • Value: uses SeriesData.value
  • Dimension index: uses the position i in seriesData (0..dimensionCount-1)
  • SeriesData.x is not used for positioning in Radar rendering (do not rely on x to represent dimensions)

Where does dimensionCount come from:

  1. Prefer Data.PolarAxes.angleAxis.labels.Count
  2. If angleAxis.labels is not configured, it uses labels from a Category Axis (see section 5)
  3. Otherwise, fall back to seriesData.Count (or the maximum count among multiple series)

5. Actual priority order for dimension labels

Runtime resolves dimension names in this priority order:

  1. polarAxes.angleAxis.labels[i]
  2. labels[i] from a AxisType.Category axis in axes[]

    3. - it prefers the Category axis that matches Data.XAxisId

  3. seriesData[i].name
  4. If none exists, it shows Dim i
Recommendation: for Radar, manage dimension names via polarAxes.angleAxis.labels. Use SeriesData.name as a fallback.

6. How radius value range is calculated

Radar radius range is calculated from SeriesData.value:

  • By default, it computes auto range from values across all Radar series
  • If you configure polarAxes.radiusAxis:

    • - autoRangeMin/autoRangeMax decides whether min/max are automatic - minValue/maxValue take effect when the corresponding auto range is disabled - autoRangeRounding rounds auto min/max to tens/hundreds/custom unit - labelFormat affects tooltip/label formatting

7. Common pitfalls and troubleshooting

  • Radar chart not visible

    • - Check coordinateSystem is Polar2D - Dimension count must be > 2 (labels or seriesData must be at least 3)

  • Dimensions do not match / order is wrong

    • - Radar does not use x. It uses seriesData list order as dimension order - Put points in seriesData in the intended dimension order

  • Hover is hard to trigger

    • - Radar pick radius is related to RadarSettings.point.size - If point.show=false, pick radius becomes 0 (almost impossible to hover)

8. Further reading

  • Series and data: 00_02-WorkflowAndLibrary.md
  • Common recipes: 04_08-CommonRecipes.md
  • FAQ: 04_09-FAQ.md