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[PERF] Replace np.column_stack with np.vstack().T #31132

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[PERF] Replace np.column_stack with np.vstack().T #31132

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0a872f9
Replace np.column_stack with np.vstack().T for performance (safe case…
crabby-rathbun Feb 11, 2026
e27a75c
Fix: Handle 1D arrays correctly in column_stack replacements
crabby-rathbun Feb 11, 2026
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12 changes: 6 additions & 6 deletions lib/matplotlib/colors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -488,7 +488,7 @@ def to_rgba_array(c, alpha=None):
" of alpha values if there are more than one"
" of each.")
if c.shape[1] == 3:
result = np.column_stack([c, np.zeros(len(c))])
result = np.hstack([c, np.zeros(len(c)).reshape(-1, 1)])
result[:, -1] = alpha if alpha is not None else 1.
elif c.shape[1] == 4:
result = c.copy()
Expand Down Expand Up @@ -527,7 +527,7 @@ def to_rgba_array(c, alpha=None):
if isinstance(c, Sequence):
lens = {len(cc) if isinstance(cc, (list, tuple)) else -1 for cc in c}
if lens == {3}:
rgba = np.column_stack([c, np.ones(len(c))])
rgba = np.hstack([c, np.ones(len(c)).reshape(-1, 1)])
elif lens == {4}:
rgba = np.array(c)
else:
Expand Down Expand Up @@ -1231,10 +1231,10 @@ def from_list(name, colors, N=256, gamma=1.0, *, bad=None, under=None, over=None
r, g, b, a = to_rgba_array(_colors).T

cdict = {
"red": np.column_stack([vals, r, r]),
"green": np.column_stack([vals, g, g]),
"blue": np.column_stack([vals, b, b]),
"alpha": np.column_stack([vals, a, a]),
"red": np.vstack([vals, r, r]).T,
"green": np.vstack([vals, g, g]).T,
"blue": np.vstack([vals, b, b]).T,
"alpha": np.vstack([vals, a, a]).T,
}

return LinearSegmentedColormap(name, cdict, N, gamma,
Expand Down
2 changes: 1 addition & 1 deletion lib/matplotlib/lines.py
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Original file line number Diff line number Diff line change
Expand Up @@ -683,7 +683,7 @@ def recache(self, always=False):
else:
y = self._y

self._xy = np.column_stack(np.broadcast_arrays(x, y)).astype(float)
self._xy = np.vstack(np.broadcast_arrays(x, y)).T.astype(float)
self._x, self._y = self._xy.T # views

self._subslice = False
Expand Down
2 changes: 1 addition & 1 deletion lib/matplotlib/patches.py
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Expand Up @@ -1131,7 +1131,7 @@ def _update_path(self):
else: # no baseline
raise ValueError('Invalid `baseline` specified')
if self.orientation == 'vertical':
xy = np.column_stack([x, y])
xy = np.vstack([x, y]).T
else:
xy = np.column_stack([y, x])
verts.append(xy)
Expand Down
2 changes: 1 addition & 1 deletion lib/matplotlib/path.py
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Expand Up @@ -802,7 +802,7 @@ def unit_regular_polygon(cls, numVertices):
# This initial rotation is to make sure the polygon always
# "points-up".
+ np.pi / 2)
verts = np.column_stack((np.cos(theta), np.sin(theta)))
verts = np.vstack((np.cos(theta), np.sin(theta))).T
path = cls(verts, closed=True, readonly=True)
if numVertices <= 16:
cls._unit_regular_polygons[numVertices] = path
Expand Down
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