Added arbitrary legend_columns for gr

[briederer]

Since I modified the code for myself I thought it would be nice to also upload so others can use it.
Especially since it is asked quite often e.g. on Discourse and #2423.
For now it is just a quick hacky solution but it works with legend_title and without. Also it differs between legend_column=-1 as a full horizontal version and legend_column=nseries where only the labels are printed horizontally but the legend_title is printed center-aligned above the series.

So maybe even if it is not merged it may help some people or be useful when switching to Plots 2.0

The following code produces the output and the figure below

data = rand(10, 3)
leg_cols = -1:4

leg_plots(; kw...) = begin
  map((leg_col -> begin
      plot(data; marker=:circle, ticks=:none, plot_title=string("legend_columns = ", leg_col), legend_columns=leg_col, kw...)
    end), leg_cols)
end
(w, h) = Plots._plot_defaults[:size]
with(scalefonts=1, size=(w, h)) do
  plot(leg_plots()..., leg_plots(legend_title="Test")...; layout=(4, 3))
end

┌ Warning: n° of legend_column=0. Assuming vertical layout.
└ @ Plots ~/.julia/dev/Plots/src/backends/gr.jl:1223
┌ Warning: n° of legend_column=4 is larger than n° of series=3
└ @ Plots ~/.julia/dev/Plots/src/backends/gr.jl:1220
┌ Warning: n° of legend_column=0. Assuming vertical layout.
└ @ Plots ~/.julia/dev/Plots/src/backends/gr.jl:1223
┌ Warning: n° of legend_column=4 is larger than n° of series=3
└ @ Plots ~/.julia/dev/Plots/src/backends/gr.jl:1220

[codecov]

Codecov Report

Base: 90.80% // Head: 90.79% // Decreases project coverage by -0.02% ⚠️

Coverage data is based on head (2d9ba02) compared to base (843b645).
Patch coverage: 85.71% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4645      +/-   ##
==========================================
- Coverage   90.80%   90.79%   -0.02%     
==========================================
  Files          41       41              
  Lines        8781     8795      +14     
==========================================
+ Hits         7974     7985      +11     
- Misses        807      810       +3     

Impacted Files	Coverage Δ
src/backends/gr.jl	91.50% <85.71%> (-0.16%)	⬇️

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[BeastyBlacksmith]

Thanks!

[lmanzanillas]

Hello,
I'm using: Plots v1.38.6, PythonPlot v1.0.2
With:
using Plots; pythonplot()
then trying to plot 4 histograms:

plot(legend=:topleft,legend_column=2)

plot!(h_depE_0d,label="polarization hor (0d)",st=:step,yaxis=:log,xlabel="Energy [keV]",framestyle = :box)

plot!(h_depE_45d,label="polarization 45 degrees",st=:step,yaxis=:log,xlabel="Energy [keV]",framestyle = :box)

plot!(h_depE_135d,label="polarization 135 degrees",st=:step,yaxis=:log,xlabel="Energy [keV]",framestyle = :box)

plot!(h_depE_90d,label="polarization ver (90d)",st=:step,yaxis=:log,xlabel="Energy [keV]",framestyle = :box)

it seems it's not working. I still get the message:
Warning: n° of legend_column=2 is not compatible with n° of series=4

When trying to plot 4 histograms. It's working when using gr()

And it seems something weird happen with the y axis when using log scale...

Any idea how to fix this?

[briederer]

Hey. This PR has implemnted the feature only for the gr backend. In all other backends only legend_columns=-1 or legend_columns=nseries for horizontal legends, and legend_columns=1 for the standard vertical layout, are supported.
So I think this would be a feature request to implement this also for other backends.