Makie.jl: Feature request: contourf

[briochemc]

I thought there was already an issue for this, but it seems not... So here it is:

It would be great to have filled contours in Makie.jl!

[aramirezreyes]

There is already if you do:

using Makie
contour(rand(10,10),fillrange=true)

Or do you mean the "convenience" function contourf explicitly?

[aramirezreyes]

Although fillrange = true behaves kind of weird:

Doing the example in here

using Makie
 N = 20
 x = LinRange(-0.3, 1, N)
 y = LinRange(-1, 0.5, N)
 z = x .* y'
contour(x, y, z, levels = 3, linewidth = 1, fillrange = true)

The result is :

Which looks weird because there is a gradient in between contour lines, which is not the usual.

The example with Plots.jl (gr backend) looks like this:

using Plots
contourf(x, y, z', levels = 3, linewidth = 1, c = :viridis)

So I think @briochemc's request makes a lot of sense.

[briochemc]

FWIW I do think having an explicit contourf would be great, because it is common among plotting libraries/languages in my (little) experience.

Bonus would be an extend keyword for the colorbar as I suggested just hours ago for Plots.jl there.

[SimonDanisch]

contour(x, y, z, levels = 3, linewidth = 1, fillrange = true) does indeed act strange since it's computed on the gpu with a very simple shader... On the up side, it's super fast :D
You should be possible to create a simple recipe that recreates what Plots.jl contourf is doing, though...

[c42f]

Well it's possible to fix the shader to do the right thing in the longer term but I haven't looked at the details. With evenly spaced levels it should be particularly easy because it's just a rescaling and a call to floor which can happen pixelwise. For arbitrary levels we'd probably need a 1D texture to look up the levels or some such thing. Depends on the detail of which data is copied over to the GPU...

[briochemc]

Has there been any update on this?

[briochemc]

For the record, there is a workaround for contourf-like plots. It's to use

heatmap(..., colormap=cgrad(..., categorical=true), interpolate=true, ...)

(thanks @AlexisRenchon and @asinghvi17?)

MWE:

x = -3:0.01:3
y = -2.5:0.1:2.5
peaks(x,y) = 3*(1-x)^2 * exp(-(x^2) - (y+1)^2) - 10*(x/5 - x^3 - y^5) * exp(-x^2-y^2) - 1/3*exp(-(x+1)^2 - y^2)
z = [peaks(x,y) for x in x, y in y] 

using AbstractPlotting
using AbstractPlotting.MakieLayout
using GLMakie
scene, layout = layoutscene()
display(scene)
ax1 = layout[1,1] = LAxis(scene)
heatmap!(ax1, x, y, z, colormap=cgrad(:starrynight, 10, categorical=true), interpolate=true)
ax2 = layout[1,2] = LAxis(scene)
heatmap!(ax2, x, y, z, colormap=:starrynight)

gives (contourf look-alike on the left, default heatmap on the right):

[aramirezreyes]

This is great! Thanks.
Are there obvious reasons not to set contourf to be an alias of this? It is better than what we already have.
By the way, why is this different than a real contourf? Is it because of the ability of setting arbitrary levels?

Edit:

Ah! I see. This is how the original example looks like. It has some weird quirks on the borders. Still a better approximation to the previous one!

[briochemc]

I seem to recall that @jkrumbiegel created an actual filled contour function for Makie not so long ago (and showed it on Slack). Any chance it can make it into the package soon?

[SimonDanisch]

https://github.com/JuliaPlots/AbstractPlotting.jl/pull/500

[jkrumbiegel]

there's even preview docs with it http://makie.juliaplots.org/previews/PR500/plotting_functions.html
although one thing I wasn't sure about yet, how are colors assigned in filled contour plots? it doesn't matter if the gaps are all equally wide, but if not?