Feature request: nan_color kwarg for meshscatter

[briochemc]

It would be great to be able to use the nan_color kwarg as implemented for heatmap by @jkrumbiegel in response to #666.

This would allow it to be combined with a meshscatter recipe for irregularly spaced grids (inspired from @ffreyer in #675 (comment)), something like that:

using GeometryBasics
@recipe(EdgyHeatMap, ex, ey, z) do scene
    Attributes(
        nan_color=:lightgray,
    )
end
# What the recipe actually does
midpoints(x) = 0.5(x[1:end-1] .+ x[2:end])
positions(ex, ey) = [Point2f0(x, y) for x in ex[1:end-1] for y in ey[1:end-1]]
sizes(dxs,dys) = [Vec2f0(dx, dy) for dx in dxs for dy in dys]
mycolors(z) = z[:]
function AbstractPlotting.plot!(p::EdgyHeatMap)
    ex = p[:ex]
    ey = p[:ey]
    z = p[:z]
    # Needs to be a mesh to not get centered?
    m = Rect2D(Point2f0(0.0), Vec2f0(1)) |> normal_mesh
    # midpoints
    midxs = lift(midpoints, ex)
    midys = lift(midpoints, ey)
    # rectangle position & size
    pos = lift(positions, ex, ey)
    dxs = lift(diff, ex)
    dys = lift(diff, ey)
    sizs = lift(sizes, dxs, dys)
    # z needs to be transposed
    Z = lift(mycolors, z)
    meshscatter!(p, pos, markersize=sizs, marker=m, color=Z, shading=false)
    p
end

and plot nice stuff like this:

but with gray NaNs! 😄

[Alexander-Barth]

@briochemc I am wondering if this PR could help in your case. (But note the PR only modifies the behavior of heatmap when using matrices as X and Y).

JuliaPlots/CairoMakie.jl#177

[briochemc]

I actually don't need this anymore since Makie's heatmap started accepting irregularly spaced (rectilinear) grids, but your PR looks really cool and I'm sure I would use it at some point, too!

[Alexander-Barth]

Maybe I misunderstand the present issue, but if you want to use grey NaNs you could do this: (with PR JuliaPlots/CairoMakie.jl#177)

using CairoMakie
x = sqrt.(0:10:100); y = sqrt.(0:10:100);
X = [x_ for x_ in x,  y_ in y]
Y = [y_ for x_ in x,  y_ in y]
A = randn(10,10); 
A[3,5] = NaN; 
fig = heatmap(X,Y,A, nan_color = RGBf0(0.8,0.8,0.8));
save("test.png",fig)

[SimonDanisch]

The thing is, you can do that with the current Makie already, with the new irregular grid heatmaps:

using CairoMakie
x = sqrt.(0:10:100); y = sqrt.(0:10:100);
A = randn(10,10); 
A[3,5] = NaN; 
heatmap(x,y,A, nan_color = RGBf0(0.8,0.8,0.8))

[Alexander-Barth]

Thanks @SimonDanisch , I did not know that 😄 Sorry for the noise.

[SimonDanisch]

btw surface also already supports matrices as arguments ;) Just needs shading false and z set to all 0, to generate that kind of heatmap..Although it will be interpolated ;)

[Alexander-Barth]

Indeed surface is pretty flexible. In our case, we can have quite a few NaNs and it would be good to avoid them to spread spatially (I can give you some examples if this would be helpful). Would you consider a PR which implements the non-interpolated option for surface ?

[asinghvi17]

A non-interpolated surface would basically be a generated mesh, with unique vertices for each grid cell. This is the only way to get per-face color into OpenGL, unfortunately.

We could have a short path for CairoMakie though!

[SimonDanisch]

nan_color is part of meshscatter these days.