Heatmap

heatmapBlock elementGraph

The same surface a contour traces, shaded instead: one expression in x AND y, grid-sampled over the visible window and drawn as a continuous wash of the mark's hue — bare where the value is low, full where it is high. The two marks compose: a heatmap under a contour is the classic landscape rendering, and @let keeps the shared expression written once. As with contour, `y` is the vertical axis, not a parameter.

Attributes

expressionRequiredImplicit

parametised-surface-expression

Also written: exp, f, func, functionMath expression for the surface's value at (x, y). Free letters beyond x and y are parameters.The head shorthand supplies it: heatmap:value

range

parametised-interval

The value window the ramp spans, e.g. `[0, 40]`; values outside clamp. Absent, the ramp spans the sampled extrema — which re-normalises as a parameter drags; an authored range holds still, exactly as an authored domain does.

invert

boolean

Flip the ramp: deep colour at LOW values. On a loss surface it is the basin that should glow.

Defaultfalse

colour

surface-colour

Also written: colormulticolour (the default) runs the full spectrum, violet low to red high; temperature is the blue → white → red wash — pair it with a symmetric `range:` to pin white at zero; any ordinary hue shades its own intensity ramp instead. Both ramps are fixed colours, identical in light and dark mode.

Defaultmulticolour

opacity

number

How heavy the wash sits over the plot.

Default0.75

hidden

boolean

Declared but not drawn — animatable, so `hidden: true !cue.to{false}(at: 2)` is its reveal.

Defaultfalse

lock

boolean

Also written: lockedA reader may not edit it on an editable graph.

Defaultfalse

parametised-number

Draw order within the pane.

Derived attributes

Computed while the element renders — read one with #id.name in attribute position or !value:#id.name() in prose, never set.

minDerived

The smallest value the surface takes over the sampled window. Cite it with !value:#id.min().

maxDerived

The largest value the surface takes over the sampled window.

Allowed in

canvas.graph { }

Examples

heatmap(expression: x*y; range: [-9, 9]; colour: temperature)

heatmap(expression: x^2 + y^2)

heatmap(expression: (x - 2)^2 + (y - 3)^2; colour: red; invert: true)

heatmap(expression: {{sse}}; opacity: 0.5)
contour(expression: {{sse}}; at: 1, 2, 4, 8, 16)

Heatmap

heatmapBlock elementGraph

Attributes

expressionRequiredImplicit

parametised-surface-expression

Also written: exp, f, func, functionMath expression for the surface's value at (x, y). Free letters beyond x and y are parameters.The head shorthand supplies it: heatmap:value

range

parametised-interval

invert

boolean

Flip the ramp: deep colour at LOW values. On a loss surface it is the basin that should glow.

Defaultfalse

colour

surface-colour

Defaultmulticolour

opacity

number

How heavy the wash sits over the plot.

Default0.75

hidden

boolean

Declared but not drawn — animatable, so `hidden: true !cue.to{false}(at: 2)` is its reveal.

Defaultfalse

lock

boolean

Also written: lockedA reader may not edit it on an editable graph.

Defaultfalse

parametised-number

Draw order within the pane.

Derived attributes

Computed while the element renders — read one with #id.name in attribute position or !value:#id.name() in prose, never set.

minDerived

The smallest value the surface takes over the sampled window. Cite it with !value:#id.min().

maxDerived

The largest value the surface takes over the sampled window.

Allowed in

canvas.graph { }

Examples

heatmap(expression: x*y; range: [-9, 9]; colour: temperature)

heatmap(expression: x^2 + y^2)

heatmap(expression: (x - 2)^2 + (y - 3)^2; colour: red; invert: true)

heatmap(expression: {{sse}}; opacity: 0.5)
contour(expression: {{sse}}; at: 1, 2, 4, 8, 16)