RadarChart

radarChart · Charts · interactive

Charts: a scale, its ticks, and a line or area drawn from data.

Import

#include "gbui/widgets/chart.hpp"

Example

Nothing is downloaded until you press it.

ChartResult radarChart(Ui& ui, const Interaction& input, std::string_view id, const std::vector<Series>& series, const RadarOptions& options = {});

One value per axis, per series, on spokes around a common centre. The chart for a profile — a handful of measures that belong together and are compared as a shape rather than read off one at a time: a skills assessment, a wine's tasting notes, one machine's five utilisation figures against another's. Everything it is good at falls apart past about eight axes, where the polygon stops being a shape and becomes a scribble. series is the same Series every other chart here takes; each value is a spoke, in order, starting at twelve o'clock and going clockwise. Hit testing is by angle, so a reader pointing anywhere along a spoke means that axis — the same rule the bars use for a category, for the same reason.

API

RadarOptions

Option	Type	Default	What it does
scale	Scale	0.0, 0.0	Fixed bounds. Left alone the chart takes them from the data — and always from zero, whatever the data says. A radar is read as an area, and area from a non-zero baseline is the same lie a truncated bar tells, told about five axes at once: two profiles a hair apart become one enormous and one tiny.
autoScale	bool	true
tickCount optional	std::optional<int>
categories	std::vector<std::string>		One name per axis, drawn outside its spoke. Fewer than there are values leaves the rest unlabelled rather than renumbering them.
size	float	240.0f	The whole chart's box, labels included.
grid	RadarGrid Web · Polygon · None	RadarGrid::Web	What is drawn behind the data: a mesh, shaded bands, or nothing.
labelRoom	float	52.0f	Room between the outermost ring and the edge, for the names. Zero draws none and gives the web the whole box.
fillAlpha	float	0.1f	Shading inside a series' polygon, when the series carries no fillAlpha of its own. Filled by default, where a line chart is not. A line is read along, and shading under two of them buries the lower one; a radar is read as a shape, and an unfilled one is a wire outline the eye has to close for itself. Lower than the 0.2 the web charting libraries settle on, and deliberately: the painter composites in linear light, where the same number covers roughly twice as much as it does in a browser blending sRGB directly.
markerRadius	float	3.0f	A dot at each vertex. Zero draws none.
hover	bool	true
valueFormat	std::string_view	"%.0f"	Printed in the readout; "%.0f" style, as std::snprintf takes.
tooltip	ChartTooltip
legend	ChartLegend
name	std::string_view		What the chart is of — "Revenue by month". A chart is the one thing on a screen a reader gets nothing from: the shapes carry all of it, and the numbers behind them are the caller's. A name and a Figure role are the least that makes it navigable, and they are not the whole answer — see the note in docs/reference/accessibility.