Function radarLayer

Reads a radar as the multi-series outline it draws.

Measured, the series carries one row per observation and one dimension per indicator -- ['indicator_0', 'indicator_1', 'indicator_2'] for a three-spoke chart -- with getName(i) answering the observation's name. The names the spokes are drawn under are not on the series at all; they are the indicator array of the radar component, which also carries the min/max ECharts resolved for each.

Every point names its own spoke in x and its own series in z, which is the shape RadarTrace is navigated by -- each spoke a column, each series a row.

What made this look unreadable, and why it is not. The refusal this replaces counted filled marks and found seven where six were expected: a two-series radar fills six vertex symbols (three per series) plus its alternating ring backgrounds, one of which (rgb(234,237,245)) is neither white nor furniture. But RadarTrace wants one selector per series, and the filled marks are one per vertex -- so they never fitted, ring background or not. What does fit is the series outline: a polyline that is stroked rather than filled, one per series, weighted and in the series colour.

stroked, unfilled, in a two-series radar
  #dbdee4          the ring outline    unweighted -> furniture
  #cfd2d7 x3       the spokes          unweighted -> furniture
  #111199 width=2  series one          <- the mark
  #229922 width=2  series two          <- the mark

which is exactly the shape markPerSeries() already finds for line, and the grid furniture is unweighted so the existing filter drops it.