Feature Request: Filled Polygon

[peterdsharpe]

Hey all,

First off - thanks for all your hard work on this beautiful visualization library. I have a feature request that would be very handy in my scientific computing work, and I wanted to submit it to you for your consideration:

Matplotlib has a very useful command to draw a 2D filled polygon (matplotlib.pyplot.fill), exhibited here:
https://matplotlib.org/3.1.1/gallery/lines_bars_and_markers/fill.html

It would be very helpful to have an equivalent command available through Plotly. As far as I'm aware, this feature does not yet exist. The closest equivalent that I could find is an SVG Path, exhibited here:
https://plot.ly/python/shapes/#svg-paths

However, the input syntax is pretty clunky, especially if one wants to plot a filled polygon with many vertices defined from, say, a NumPy ndarray:

        go.layout.Shape(
            type="path",
            path=" M 3,7 L2,8 L2,9 L3,10, L4,10 L5,9 L5,8 L4,7 Z",
            fillcolor="PaleTurquoise",
            line_color="LightSeaGreen",
        ),

A more streamlined interface, with syntax that lends itself to scientific computing (like matplotlib.pyplot.fill), would be greatly appreciated. Is this a feature the Plotly team would consider adding?

Thank you so much!
-Peter

[empet]

@peterdsharpe It's not so awful to define a filled polygon with many points. You can use f-string concatenation:

n_points =50
polygon = f'M {x[0]}, {y[0]}'
for k in range(1, n_points):
    polygon += f' L{x[k]}, {y[k]}'
polygon += ' Z'

fig = go.Figure(go.Scatter())
fig.update_layout(width=600, height=600,
                  shapes=[dict(path =polygon,
                          fillcolor='RoyalBlue',
                          line_width=2,
                          line_color='RoyalBlue')])

[nicolaskruchten]

You can also use a scatter trace with the fill="toself" option to create closed, filled shapes out of arrays. This approach gives you hover-labels which you can fill with useful information.

[nicolaskruchten]

A single trace can also encode many shapes if you interrupt the series with None:

[nicolaskruchten]

@Mahdis-z could you please add something like the two examples above to https://plot.ly/python/shapes/ with a little explanation about the difference between this approach and layout.shapes?

[peterdsharpe]

@empet, I'm well aware that a string concatenation with SVG shapes is possible, but as previously mentioned, it's clunky and not very scalable.

@nicolaskruchten, thank you so much for the scatter suggestion - this is perfect and exactly what I was looking for! Not sure how I missed the fill="toself" option in the documentation! Thanks!

[nicolaskruchten]

Not sure how I missed the fill="toself" option in the documentation

I think that's on us... I don't think it's really front and center!