Manual discrete colormap

[jfb-h]

Is it possible to use a manual discrete colormap as described in the manual for the python version?

E.g. like so, which errors:

df = DataFrame(x=rand(100), y=rand(100), g=rand(["a", "b", "c"], 100))

cmap = Dict(
    "a" => "red", 
    "b" => "blue",
    "c" => "green"
)

sc = scatter(df, x=:x, y=:y, group=:g, mode="markers", color_discrete_map=cmap)

I couldn't find anything in the documentation and tried a bunch of different things but nothing did the trick.

[empet]

The colorscale should look like this:

cmap = [[0.0, "rgb(255, 0, 0)"],
        [0.5, "rgb(0, 255, 0)"],
        [1.0,  "rgb(0, 0, 255)"]]

i.e. it is defined as an 3-element Array{Array{Any,1},1}.

You can give the color codes in hex format, too:

plasma = [[0.0, "#0c0786"],
          [0.1, "#40039c"],
          [0.2, "#6a00a7"],
          [0.3, "#8f0da3"],
          [0.4, "#b02a8f"],
          [0.5, "#cb4777"],
          [0.6, "#e06461"],
          [0.7, "#f2844b"],
          [0.8, "#fca635"],
          [0.9, "#fcce25"],
          [1.0, "#eff821"]] 

The latter example is the default colorscale in the Python version.

[jfb-h]

Thanks, good to know it should be an array not a dict! However, this does not seem to help with the discrete color mapping problem. Do you know if there's a keyword argument for that also in Julia?

[empet]

Could you explain what do you mean by discrete colorscale? Is this discrete colorscale https://community.plotly.com/t/colors-for-discrete-ranges-in-heatmaps/7780 what you are looking for?

[jfb-h]

The python manual on discrete color has a section (pretty far down) which shows how to directly assign colors to levels of a grouping variable. Here's the code snippet:

import plotly.express as px
df = px.data.gapminder().query("year == 2007")
fig = px.bar(df, y="continent", x="pop", color="continent", orientation="h", hover_name="country",
             color_discrete_map={
                "Europe": "red",
                "Asia": "green",
                "Americas": "blue",
                "Oceania": "goldenrod",
                "Africa": "magenta"},
             title="Explicit color mapping")

fig.show()

I would like to reproduce that in Julia, i.e. I'm looking for an equivalent to the color_discrete_map keyword.

[empet]

Plotly express is a wrapper for plotly.py that exposes a simple syntax for complex charts. Behind the scenes it performs the same computations like in the forum answers above. There is no Julia library that can imitate plotly express functions.

[jfb-h]

I see, thanks. I thought as PlotlyJS.jl exposes some similar features (e.g. convenience plotting with DataFrames) this might also be available.