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Add RuntimeWarning guard around division-by-zero #22628

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Merged
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Mar 31, 2022
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Add RuntimeWarning guard around division-by-zero #22628

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10 changes: 7 additions & 3 deletions lib/mpl_toolkits/mplot3d/proj3d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -14,14 +14,18 @@ def _line2d_seg_dist(p1, p2, p0):
p0[1] = y(s)

intersection point p = p1 + u*(p2-p1)
and intersection point lies within segment if u is between 0 and 1
and intersection point lies within segment if u is between 0 and 1.

If p1 and p2 are identical, the distance between them and p0 is returned.
"""
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@timhoffm timhoffm Mar 18, 2022 •
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Your solution is technically correct. However, the issue is more a logical one rather than a technical division-by-zero problem. Therefore, I'd go with the following and leave all the original code unchanged in place.

Suggested change
"""
If p1 and p2 are identical, the distance between them and p0 is returned.
"""
if np.all(p1 == p2):
return np.hypot(p1[0] - p0[0], p1[1] - p0[1])

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Added the docs and removed the comment. (Kept the solution with intermediate results.)

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Kept the solution with intermediate results.

@oscargus: What is the motivation for keeping this? It would be nice to give a reason if you dismiss a suggestion. I find the separation of the special case and using explicit values there more clear, but can be convinced otherwise.

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Just wanted to avoid duplicate code (and was a bit unsure what the effect of np.asarray was).

But I see your point about separation as well. And will try to motivate better in the future.


x21 = p2[0] - p1[0]
y21 = p2[1] - p1[1]
x01 = np.asarray(p0[0]) - p1[0]
y01 = np.asarray(p0[1]) - p1[1]
if np.all(p1 == p2):
return np.hypot(x01, y01)

x21 = p2[0] - p1[0]
y21 = p2[1] - p1[1]
u = (x01*x21 + y01*y21) / (x21**2 + y21**2)
u = np.clip(u, 0, 1)
d = np.hypot(x01 - u*x21, y01 - u*y21)
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10 changes: 10 additions & 0 deletions lib/mpl_toolkits/tests/test_mplot3d.py
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Expand Up @@ -1002,6 +1002,16 @@ def test_lines_dists():
ax.set_ylim(0, 300)


def test_lines_dists_nowarning():
# Smoke test to see that no RuntimeWarning is emitted when two first
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would it be preferable to test a user-facing API rather than the private methods?

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This is mostly called through mouse callbacks so it is annoying to get public API tests that exercise this.

# arguments are the same, see GH#22624
p0 = (10, 30)
p1 = (20, 150)
proj3d._line2d_seg_dist(p0, p0, p1)
p0 = np.array(p0)
proj3d._line2d_seg_dist(p0, p0, p1)


def test_autoscale():
fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
ax.margins(x=0, y=.1, z=.2)
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