Disappointing Behavior with colors and Guide.manual_color_key

[Nosferican]

Guide.manual_color_key renders an additional legend instead of replacing the default one from colors.

[tlnagy]

Can you post a minimal code example for us to reproduce?

[Nosferican]

Here it is:

using DataFrames
using RDatasets
using Gadfly
iris = dataset("datasets", "iris")

Using color as usual:

Plot = plot(iris, x = :SepalWidth, y = :SepalLength, color = :Species, Geom.point)

Now I attempt to use Guide.manual_color_key along color.

Plot = plot(iris, x = :SepalWidth, y = :SepalLength, color = :Species, Geom.point,
Guide.manual_color_key("Not Species", ["setosa?", "versicolor?", "virginica?"],
["red", "green", "blue"]))

I suggest that Guide.manual_color_key replace the legend at all or add an option to either modify the one by color or replace it completely (the default behavior).

[Mattriks]

How about:

cscale = Scale.color_discrete_manual(colorant"red", colorant"green", colorant"blue")
p = plot(iris, x = :SepalWidth, y = :SepalLength, color = :Species, Geom.point, 
    cscale, Guide.colorkey("Iris")
)

See Guide.manual_color_key for an example of the sort of plot its designed for.

[Nosferican]

That's one alternative. I needed to change the label values as well to a string that it is not supported for column names in data frames so defining the Scale.color_discrete_manual would not be a complete solution for me, e.g. (p = 0.25). I ended up having to do the long way and make a layer for each one so I could use the Guide.manual_color_key and not depend on color to create the individual geoms for each group of y.

[Mattriks]

So the issue here seems to be what to do about difficult factor/level/label names in DataFrames. The suggestion here is to change the factor/level/label names after the dataframe has been converted to long format. For example:

d = Dict{String,String}("setosa"=>"p=0.1","versicolor"=>"p=0.2", "virginica"=>"p=0.3")
# Add a new variable to the dataframe:
iris[:g] = map(x -> d[x], iris[:Species])

p = plot(iris, x = :SepalWidth, y = :SepalLength, color = :g, Geom.point, 
    cscale, Guide.colorkey("Iris")
)

[Nosferican]

I like that approach as it is a good workaround and in many cases preferred to creating the different layers. However, I still think it is worthy to address the compatibility issue between color and Scale.color_discrete_manual and the double legend issue.

[xiaohk]

Yes, I agree with @Nosferican. It would be great if Guide.manual_color_key can overwrite the color key legend generated by color or Scale.color_discrete_manual .

[Nosferican]

Any updates on this front? An alternative would be to have the Theme(key_position::Symbol = :right) accept a vector of positions matching the number of legends. That way, one can potentially suppress any or display them at different positions.

On a potentially related aspect, for Functions and Expressions the default f1, f2, ... names will almost surely be better served with more useful labels. I couldn't find an issue addressing it, but it might be related to this. In case there isn't a way to change the default names a custom color key might be needed and it would suffer from the same issue.

[Mattriks]

Not yet. Another possible option here is to give each layer control of its own key, like this (atm this has no effect):

p = plot(
    layer([sin, cos], 0, 25, Theme(key_position=:none))
    )

[Mattriks]

Yes for Functions and Expressions, currently the function names are fixed here.

[Mattriks]

With Gadfly 0.6.5 the colorkey labels can now be changed directly from Guide.colorkey. Returning to the minimal example above:

p= plot(iris, Geom.point,
    x = :SepalWidth, y = :SepalLength, color = :Species, 
    Guide.colorkey(title="Not Species", labels=["setosa?", "versicolor?", "virginica?"])
    )

So the original issue here doesn't seem to apply anymore. Also there are reasons that a user might want to actually have 2 keys: Guide.colorkey and Guide.manual_color_key e.g. #1098