Bars

Property	Default	Meaning
values	[]	Bar endpoints
positions	Indices	Bar centers; must match values
bases	0	Scalar, array, or callback for bar baselines
bar-width	0.8	Scalar, array, or callback for widths in data units
direction	"vertical"	Vertical or horizontal bars
border-radius	0	Scalar, elliptical pair, or side/corner object in layout units
styles	—	Per-bar style array or (value, index) => style callback; may override border-radius
space	Automatic	Use ambient data coordinates or local geometry

Draw bars from values. positions supplies centers (default indices starting at zero), bases defaults to zero, and bar-width to 0.8 data units. bases and bar-width accept a scalar, a same-length array, or (value,index) function. Values are endpoints, not lengths relative to a base.

direction defaults to vertical, or horizontal for HBars. Negative values work in either direction. Widths and bases contribute to inferred limits. Nonfinite values are omitted without shifting category indices.

styles accepts a same-length array or (value,index) function returning style objects, evaluated once at construction. Defaults: blue fill, no stroke. border-radius rounds corners in layout units such as em(0.25). Use Graph or Plot for data coordinates.

Return border_radius in a style entry to override the shared radius for that bar: styles={(value) => ({ border_radius: px(abs(value) / 4) })}. Style arrays support the same field. An omitted radius inherits the shared value; border_radius: 0 keeps that bar square. Callbacks receive the original value and index, skipping nonfinite values, and are not rerun during resizing. Per-bar radii accept all forms below; their em lengths use the bar's resolved font size.

Radius also accepts an elliptical [x, y] / { x, y } pair or a side/corner object using t, b, l, r, tl, tr, bl, and br, as on Box. Each entry can be a scalar or pair. For positive vertical bars, round only the top with border-radius={{ t: em(0.5) }} to keep the baseline square. For positive horizontal bars, use border-radius={{ r: em(0.5) }}.

Sides refer to screen edges, including for negative values and flipped axes. Use b for the exposed end of a negative vertical bar and l for a negative horizontal bar under the default axes. Scalar fractions use the mark allocation's shorter side; pairs use its width and height. Each bar then caps the resolved radii at half its own dimensions. px/em radii keep the same size across bars.