The magnitude at this x, or null where the series has a position but no
reading.
A gap is not a zero. seaborn.pointplot pads a hue level missing from one
category so its estimate lines stay the same length, and a producer that
meets a break in a series has nowhere else to put it. Number(null) is
0, which would make the gap sound like a real low point, let it be
reached as the row's minimum, and pull the range every other point's pitch
is scaled against — the same trap toBarValue was written for (#925).
null rather than a non-finite number because the payload has to survive
JSON.parse: json.dumps writes NaN and Infinity as bare tokens that
are legal JavaScript and invalid JSON, and a producer emitting one stops
the chart initialising at all (xability/py-maidr#427).
OptionalzOptionallabelOrdinal level name announced in place of the raw numeric y, for a chart
whose y axis is a category rather than a magnitude — a hypnogram's sleep
stages, a Likert response, a severity grade. y stays numeric because it
drives sonification, braille and the min/max range, so the human-readable
name has to travel alongside it.
An empty string counts as absent, so a producer that emits '' for an
unnamed level gets the numeric announcement rather than a blank one.
Omitting it entirely is the right shape for a continuous y.
OptionalyLower bound of the uncertainty around y, when the chart draws one.
A fitted curve almost always comes with a band, and it is the reason the
curve is drawn rather than a plain line: geom_smooth(se = TRUE) and
sns.regplot both default to one. Carried on the sample rather than in a
layer of its own so a reader hears the value and its interval at the same
x — the comparison a band exists for is whether the trend is
distinguishable from flat, and that cannot be made by navigating two
layers in turn.
Named to match ErrorBarPoint, so a producer that already computes an interval emits the same keys wherever it puts them.
Both bounds are optional and independent: a one-sided interval is a real chart, and a sample missing its bounds still carries its value.
OptionalyUpper bound of the uncertainty around y. See LinePoint.yMin.
OptionallevelThe value of the field along this curve.
Constant down a curve and carried on every point of it, the way z is:
the grammar's unit is the point, and a producer emitting a flat list has
nowhere else to put it.
One point on one iso-value curve of a contour plot.
A contour draws a scalar field as curves of constant value, so a layer is one curve per level -- structurally the multi-line layer LineTrace already navigates. What makes it a type of its own is that the level is a first-class object rather than a colour: the questions a reader brings are how many levels there are, where the 0.05 contour runs, and how far apart the curves are here.