heatmap

heatmap(x, y, values)
heatmap(values)

Examples

Two vectors and a matrix

using CairoMakie



xs = range(0, 10, length = 25)
ys = range(0, 15, length = 25)
zs = [cos(x) * sin(y) for x in xs, y in ys]

heatmap(xs, ys, zs)

Two ranges and a function

using CairoMakie


function mandelbrot(x, y)
    z = c = x + y*im
    for i in 1:30.0; abs(z) > 2 && return i; z = z^2 + c; end; 0
end

heatmap(-2:0.001:1, -1.1:0.001:1.1, mandelbrot,
    colormap = Reverse(:deep))

Three vectors

There must be no duplicate combinations of x and y, but it is allowed to leave out values.

using CairoMakie



xs = [1, 2, 3, 1, 2, 3, 1, 2, 3]
ys = [1, 1, 1, 2, 2, 2, 3, 3, 3]
zs = [1, 2, 3, 4, 5, 6, 7, 8, NaN]

heatmap(xs, ys, zs)

Colorbar for single heatmap

To get a scale for what the colors represent, add a colorbar. The colorbar is placed within the figure in the first argument, and the scale and colormap can be conveniently set by passing the relevant heatmap to it.

using CairoMakie


xs = range(0, 2π, length=100)
ys = range(0, 2π, length=100)
zs = [sin(x*y) for x in xs, y in ys]

fig, ax, hm = heatmap(xs, ys, zs)
Colorbar(fig[:, end+1], hm)

fig

Colorbar for multiple heatmaps

When there are several heatmaps in a single figure, it can be useful to have a single colorbar represent all of them. It is important to then have synchronized scales and colormaps for the heatmaps and colorbar. This is done by setting the colorrange explicitly, so that it is independent of the data shown by that particular heatmap.

Since the heatmaps in the example below have the same colorrange and colormap, any of them can be passed to Colorbar to give the colorbar the same attributes. Alternativly, the colorbar attributes can be set explicitly.

using CairoMakie


xs = range(0, 2π, length=100)
ys = range(0, 2π, length=100)
zs1 = [sin(x*y) for x in xs, y in ys]
zs2 = [2sin(x*y) for x in xs, y in ys]

joint_limits = (-2, 2)  # here we pick the limits manually for simplicity instead of computing them

fig, ax1, hm1 = heatmap(xs, ys, zs1,  colorrange = joint_limits)
ax2, hm2 = heatmap(fig[1, end+1], xs, ys, zs2, colorrange = joint_limits)

Colorbar(fig[:, end+1], hm1)                     # These three
Colorbar(fig[:, end+1], hm2)                     # colorbars are
Colorbar(fig[:, end+1], colorrange = joint_limits)  # equivalent

fig

Using a custom colorscale

One can define a custom (color)scale using the ReversibleScale type. When the transformation is simple enough (log, sqrt, ...), the inverse transform is automatically deduced.

using CairoMakie

x = 10.0.^(1:0.1:4)
y = 1.0:0.1:5.0
z = broadcast((x, y) -> x - 10, x, y')

scale = ReversibleScale(x -> asinh(x / 2) / log(10), x -> 2sinh(log(10) * x))
fig, ax, hm = heatmap(x, y, z; colorscale = scale, axis = (; xscale = scale))
Colorbar(fig[1, 2], hm)

fig