How to subtract a scatterplot object from a polyshape object

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Kurt
Kurt 2025-4-1
评论： Kurt 2025-4-10
In my app I am defining polyshapes that represent satellite scan regions on Earth. I know how to subtract polyshapes from each other, for example along coastlines. Now I have a set of scatterplots that represent things such as sea ice, that I also need to subtract from the polyshape scan regions, something like this:
The pink represents the satellite scan region, and the blue is the scatterplot. I need to subtract the scatterplot area from the polyshape scan region. I know scatterplots do not have "area" per se, but perhaps we can define a boundary?
Is there a way to convert a scatterplot to a polyshape? I have seen several discussions here on scatterplots, but nothing quite like this situation. The closest I have come is this answer:
https://www.mathworks.com/matlabcentral/answers/472879-surface-from-scatter-3-plot
Thanks!

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Walter Roberson
Walter Roberson 2025-4-8
You can retrieve the XData and YData from the scatter plot, and pass the resulting points to boundary or alphaShape to trace around the outside of the set of points. This will give you a refined set of points that you can use to create another polyshape that you can then subtract from the original polyshape.
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Walter Roberson
Walter Roberson 2025-4-10
Well you could do something like kmeans clustering and select each cluster and boundary() it individually.
... Now you just need a way of automatically determining the correct number of clusters...
Kurt
Kurt 2025-4-10
Is there a way to divide a polyshape into its separate regions? I didn't see anything.

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peak
peak 2025-4-1
编辑：Steven Lord 2025-4-1
The scatterplot is shown in blue, while the satellite scan region is shown in pink. The scatterplot area must be subtracted from the polyshape scan region. https://www.mathworks.com/matlabcentral/answers/472879-surface-from-scatter-3-plot
[SL: Removed link that appeared to be unrelated to the question.]
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Kurt
Kurt 2025-4-1
编辑：Kurt 2025-4-8
Can you elaborate on this ? I don't see a solution in the link. I'm trying to work with polyshapes, which are not quite the same thing as surface plots.
Also, my scatterplot data contains NaNs, which don't work well with mesh objects.

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