Implement `range_color`

[tpvasconcelos]

Add support for range_color

For example, if a color range of [100, 200] is used with the ["blue", "green", "red"] color scale, then any instance with a color value of 100 or less will be blue, and 200 or more will be red. Anything in between will be interpolated as usual.

Ref: https://plotly.com/python/colorscales/#explicitly-setting-a-color-range

[CaioSilvaUT]

Hello, I'm a student from UTFPR in Brazil, and I'm taking a class where I need to contribute to open source issues. I would like to know if I can take on this issue to work on.

[tpvasconcelos]

@CaioSilvaUT boas! Sure, I'd be happy to guide you :)

Let me know if you need help getting started.

And please take a quick look at our contributing guide to ensure you get a working development environment from the start 🚀

[CaioSilvaUT]

@tpvasconcelos Sorry to bother you, but I have some questions about completing this issue. If possible, I would like to get in touch via email or something like that, even a Google Meet call if necessary.
I've already made a draft of the range_color function using plotly example, but I'm having trouble figuring out where to place it in this repository. I’ve never worked with such a large repository before.

[tpvasconcelos]

That's understandable. From the issue's description it is not clear exactly how this feature should be implemented. Here are my thoughts on it at first glance.

• Maybe we should narrow this down to only apply to colormode='fillgradient' for now, since it doesn't make sense in the context on index-based colormodes and it's not very obvious that this would be useful in the mean-based colormodes either.
  • If we do this, it should be clearly documented in the ridgeplot() docstring!
• range_color should be added as a new parameter to the ridgeplot() function, and then passed through to create_ridgeplot() and finally to ColoringContext()
• For the area trace (AreaTrace), the values will likely have to be passed to the Fillgradient's start and stop parameters. I'm not sure about this tho... Can you investigate?
• For the bar trace (BarTrace), the p should be set to 0 for x values smaller than the lower range and 1 for x values larger than the upper range

Let me know if something is not clear or if you get stuck somewhere!