How to plot in grayscale with gadfly?

Specific Domains Visualization
1

Hi,

I have some code roughly like this:

using DataFrames
using Gadfly
df = DataFrame(
    :percent_barrier => sqrt.(rand(100)) .* 100,
    :stop_reason => ifelse.(rand(100) .> 0.75, "Solved", "Timeout")
)
plot(
    df, x = "percent_barrier", color="stop_reason", Geom.histogram(;bincount = 10),
    Gadfly.Guide.xlabel("Time spent solving barrier (10% bins)"),
    Gadfly.Guide.ylabel("Amount of instances"),
    Guide.colorkey(; title = "Stop reason")
)

Which generates the following image:

example

In R, I remember that I just needed to pass some object/flag for it to use grayscale and it was done. I am, however, not finding an easy answer for Gadfly. There is some parameter that I can pass to any plot that use more colors than just black to make it grayscale?

2

no there is not an easy way. it is possible though to specify all the color defaults with a custom Theme. Gadlfy has two built-in “named” themes: Themes · Gadfly.jl. it would seem useful to have a greyscale theme too. care to submit a PR?

3

I have read the description of the Gadfly.Theme, and it seems like more than I can handle right now, the following description of a field has also diminished my hopes:

discrete_colormap

A new Theme field, in development. Currently only works with Guide.manual_discrete_key and Guide.manual_color_key. (Function)

So I am not sure if the tools to implement a pervasive grayscale Theme exist currently.

4

The current way to change to a discrete gray scale for a single plot is:

plot(df, x = "percent_barrier", color="stop_reason", 
    Geom.histogram(;bincount = 10),
    Scale.color_discrete_manual("gray10","gray50"),

Changing colorscales via Theme currently has some issues (see link in https://github.com/GiovineItalia/Gadfly.jl/pull/1118). But these changes are now being rolled out in other PRs (as you see noted with discrete_colormap). The tables in the Gadfly Tutorial show the current status.