Colorbar for contour plot with uneven spacing of contour lines

Specific Domains Visualization
1

Hi,
I’m trying to add a colorbar for a contour plot with uneven spacing between the contour lines. The contour plot

using CairoMakie

fig = let 
    fig = Figure()
    ax = Axis(fig[1, 1])

    xrg = 0.0:0.01:1.0
    yrg = -1.0:0.1:1.0

    z(x, y) = x.^2 .+ y.^2

    zvals = zeros(length(xrg), length(yrg))
    for (ix_x, x) ∈ enumerate(xrg)
        for (ix_y, y) ∈ enumerate(yrg)
            zvals[ix_x, ix_y] = z(x,y)
        end
    end

    cf = contour!(ax, xrg, yrg, zvals, levels=cat(0.1:0.05:0.3, 0.4:0.1:1.0, dims=1), labels=true, colormap=:hsv)
    #Colorbar(fig[1, 2], cf)
    fig
end

When I naively try to add a colorbar I get the error

ERROR: Multiple colormaps found for plot MakieCore.Text{Tuple{Vector{Point{2, Float32}}}}, please specify which one to use manually. Please overload `Makie.extract_colormap(::MakieCore.Text{Tuple{Vector{Point{2, Float32}}}})` to allow for the automatical creation of a Colorbar.

I also tried wrapping into a categorical colormap,, but get the same error.

Is there a good way of adding the colorbar with levels specified in the contour plot?

2

This code actually does what I need:

    fig = Figure()
    ax = Axis(fig[1, 1])

    xrg = 0.0:0.01:1.0
    yrg = -1.0:0.1:1.0

    z(x, y) = x.^2 .+ y.^2

    zvals = zeros(length(xrg), length(yrg))
    for (ix_x, x) ∈ enumerate(xrg)
        for (ix_y, y) ∈ enumerate(yrg)
            zvals[ix_x, ix_y] = z(x,y)
        end
    end

    c_levels = cat(0.0:0.05:0.3, 0.4:0.1:1.0, dims=1)
    cc = cgrad(:matter, c_levels, categorical=true)

    cf = contour!(ax, xrg, yrg, zvals, levels=c_levels, labels=true, colormap=cc)
    Colorbar(fig[1, 2], colormap=cc, ticks=c_levels)
    fig

Posting here always gives me the good ideas :slight_smile:

1 Like
3

FYI you can use

 zvals = [z(x,y) for x in xrg, y in yrg]
4

Please open an issue about this in the Makie repo! The initial code should have worked, and since it didn’t it’s a bug.