I have a set of unstructured (x,y) points which I would like to

compute a boundary polygon for. I don't want the convex hull.

I was able to use matplotlib.tri to get a Delaunay triangulation for

my points by following the examples online, but I'm having trouble

masking everything but the triangles with a boundary edge.

Additionally, once I get this, I'm not clear on how to plot just the

boundary.

Here is what it seems like the mask should be, assume triang comes

from matplotlib.tri.Triangulation().

mask = np.where(np.where(triang.neighbors < 0, 0, 1).all(axis=1), 1, 0)

triang.set_mask(mask)

but, when I plot triang using plot.triplot(), or plt.plot() to plot

the edges, I am getting a bunch of extra stuff that isn't just the

boundary triangles/edges.

Anybody have example code for properly masking and plotting only the

boundary edges?

~Luke

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