ax.scatter Ignores "cmap" Argument When 'c' Argument is a List of Values Between 0 and 1

[chudlerk]

Hello,

When I run the following simple script:

import ultraplot as uplt
fig,ax=uplt.subplots()
ax.scatter(
    [1.0, 2.0, 3.0, 4.0],
    [1.0, 2.0, 3.0, 4.0],
    c=[.1, .2, .3, .4], 
    cmap='turbo',
    )

I get the following warning:
UltraPlotWarning: Ignoring unused keyword arg(s): {'cmap': 'turbo'}
and the resulting scatter plot does not use the specified colormap.

If I do the same thing with matplotlib, it works fine:

import matplotlib.pyplot as plt
fig,ax=plt.subplots()
ax.scatter(
    [1.0, 2.0, 3.0, 4.0],
    [1.0, 2.0, 3.0, 4.0],
    c=[0.1, 0.2, 0.3, 0.4],
    cmap='turbo',
    )

I am using the latest version of ultraplot (2.1.3)

[chudlerk]

Ahh ok, I did some more digging and I'm realizing that this issue only happens when the c argument is values between 0 and 1 and there are only 3-4 elements in the lists. So it seems like the issue probably has something to do with ultraplot trying to interpret the c argument as RGB/RGBA values? My hacky workaround now is to just pad the list with NaNs so that it is always at least 5 elements long. But maybe there is a more elegant solution.

[cvanelteren]

By default it will pick either or when selecting the inputs. That is it will read c, color, colors or cmap as mutually exclusive and pick the first. We can make this behave similar to matplotlib.

I haven't run into this particular edge case yet, but can see the value of it.

[cvanelteren]

Away on a trip now but can hash this out next week, or ofc pr it and I can review it.

[cvanelteren]

@chudlerk fixed on main