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pythoncolormapholoviewsdatashader

Holoviews change datashader colormap

I'm trying to change the colormap used by datashader.

I tried this:

datashade(scatter, cmap='Reds')

Where scatter is an hv.Scatter element. This doesn't work because datashader expects an iterable or a function that returns colors. As such, this works:

datashade(scatter, cmap=['blue'])

So how can I take the 'Reds' colormap and convert it into something datashader can use?

Thank you.

Solution

  • Right; you can't pass the string name of a colormap to Datashader's cmap argument, because Datashader interprets a single string as the name of a single color, constructing a colormap from it by setting the R,G,B channels to that color and then varying the alpha channel. If you want a colormap, either pass a list of colors (as used by Bokeh for its palettes) or a Matplotlib colormap object (not the string name) to cmap:

    from matplotlib import cm
datashade(scatter, cmap=cm.Reds)