Position along the main axis.
OptionalyThe estimate itself: a mean, a median, a fitted value.
Absent on a band that draws only bounds. ForestPoint re-declares it required, because a forest plot's whole reading is whether the interval crosses the null relative to the estimate — so the shape that needs it says so, rather than every reader of this one assuming it.
OptionalyAbsolute lower bound of the interval, when the chart draws one.
OptionalyAbsolute upper bound of the interval, when the chart draws one.
OptionalzName of the group this estimate belongs to, for a chart drawing an interval per group at each category.
Named to match LinePoint.z and carried for the same reason. A dodged error bar over two treatments puts two estimates at every category, and without this they arrive as two readings of one name with nothing telling them apart. The grouping cannot be recovered from emission order, because nothing states that order — so the comparison the chart exists to support, whether one group's interval overlaps another's, is the thing that goes missing (#942).
Meaningful on the grouped shape, ErrorBarPoint[][], where every point
in a series carries the same value. A single-series chart has one group
and needs no name for it.
One estimate with the interval drawn around it.
The interval is the reason this is a point shape of its own rather than a scatter point: a chart drawn this way carries two magnitudes at every sample — the estimate, and how far from it the data is consistent with — and a reading that names only the first drops the part most statistical graphics are drawn to show.
lowerandupperare absolute positions on the value axis, not offsets fromy. Producers disagree about which they hand out (matplotlib'syerris an offset, Vega-Lite'serrorbarcomputes bounds), so the schema fixes one and each adapter converts to it.The bounds are optional and independently so: a one-sided interval — an upper bound with no lower, say — is a real chart, and dropping the point for want of its other half would lose the estimate too.
The estimate is optional for the mirror-image reason. A band with two bounds and nothing between them is a real chart too — Highcharts draws it as
arearange, and the same shape arrives fromPlot.areaYwithy1/y2, fromgeom_ribbon, and fromfill_betweenwithout a centre line. There is no honest number to put here for one: the midpoint is a value the chart never draws, and either bound announced as the estimate loses the other and implies a point reading the chart does not make (#1047).