Single colorbar for heatmap grid layout

General Usage
,
1

Take for example:

using Plots

plot(
    heatmap(rand(10,10)),
    heatmap(rand(10,10)),
    heatmap(rand(10,10)),
    heatmap(rand(10,10));
    layout=4
)

heatmaps

How could it be possible to have a single colorbar for all heatmaps?

2

If you don’t mind trying out a different package, this is one of the problems why I wrote MakieLayout http://makie.juliaplots.org/stable/makielayout/tutorial.html

Other than that, I think people have come up with hacks to solve your problem in Plots, too, maybe you can find other threads in this discourse as well

1 Like
3

Yes this isn’t easily possible in Plots.jl, as the plots are produced independently and there aren’t currently any figure level arguments (like figure title, legend etc.)

The usual hacks that I think Jules refers to are basically adding another subplot to your figure, which would just have the colorbar, and then do legend = :none on the heatmaps.

If you don’t mind one subplot being sized differently you could just do:

plot([[heatmap(rand(10, 10), legend = :none) for _ ∈ 1:3]; heatmap(rand(10, 10))]...)

image

4

This does what you want but not directly.

julia> ps = [heatmap(rand(10,10), legend=:none) for i=1:2,j=1:2] # Make heatmaps without legends
2×2 Matrix{Plots.Plot{Plots.GRBackend}}:
 Plot{Plots.GRBackend() n=1}  Plot{Plots.GRBackend() n=1}
 Plot{Plots.GRBackend() n=1}  Plot{Plots.GRBackend() n=1}

julia> l = @layout[grid(2,2) a{0.05w}] # Stack a layout that rightmost one is for color bar
Plots.GridLayout(1, 2)

julia> p = plot(ps..., heatmap((0:0.01:1).*ones(101,1), legend=:none, xticks=:none, yticks=(1:10:101, string.(0:0.1:1))), layout=l) # Plot them set y values of color bar accordingly

julia> savefig(p, "plot.png")

plot

4 Likes
5

Yes!! I was trying to do the same @layout trick, but couldn’t figure out how to make the single large colorbar. A smooth heatmap is very clever!