Feature Request: manually set colorbar without mappable

4 thoughts on “Feature Request: manually set colorbar without mappable”

1. Having a common colorbar for multiple axes is part of what I was looking for, but what I’d really like is the ability to explicitly set the limits of the colorbar via arguments to the colorbar method.

2. Example of making a colorbar that is not tied to anything else:
   http://matplotlib.org/examples/api/colorbar_only.html
   “Mappable” refers to an Artist subclass that inherits from the ScalarMappable mixin:
   http://matplotlib.org/api/cm_api.html

3. Close if you want to — but just to clarify:

   The point of the original issue was to request that the interface be simplified. Yes, there are ways to create a colorbar on e.g. line plots:

   sm = plt.cm.ScalarMappable(cmap=my_cmap, norm=plt.Normalize(vmin=0, vmax=1))
   sm._A = []
   plt.colorbar(sm)

   But this isn’t intuitive/easy for users — you more or less need to go to stackoverflow or dig deep into the documentation/examples to figure this out. So the proposal/feature request was to make this a one-liner and have matplotlib execute something like the above code under the hood (without the user needing to know what a ScalarMappable is).

4. Well my use case was an animation where the lines were changing color over time. For example, representing flow in a network, or electricity.

   I wanted a colorbar on the side to show the range of the colormap I was using. So, for example, if the maximum flow allowable was 1.0, it would be nice to just specify:

   plt.colorbar(cmap=cm.jet,min=0.0,max=1.0)

   Edit: Also, while the LineCollection example is a nice one, it isn’t immediately obvious to the common user that it exists and how to take advantage of it. Whereas I think the above one-liner is likely something people would try off the bat (especially if the min/max options are listed in the documentation for colorbar).

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