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Colorbar grid position #18575

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Merged
merged 18 commits into from
Oct 16, 2020
Merged

Colorbar grid position #18575

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9ac3c86
update colorbar.py make_axes_gridspec
Mar 3, 2020
82486c5
Update colorbar.py
Mar 3, 2020
a55b35c
fix `wh_ratios` orientation in `make_axes_gridspec`
Apr 7, 2020
2c2a4ae
add tests for cbar anchor
May 23, 2020
d1e6266
rewrite test and factored out duplicate code
Sep 26, 2020
7bf9180
Merge branch 'master' into colorbarGridPosition
Sep 26, 2020
a4e32ee
modify the gallery example of colorbar
Sep 26, 2020
b356530
Merge branch 'colorbarGridPosition' of https://github.com/ShawnChen19…
Sep 26, 2020
979ecee
flake8 compliance
Sep 26, 2020
9365767
flake8 compliance
Sep 26, 2020
74f5f48
add different senarioes for anchored_cbar_position_using_specgrid
Sep 27, 2020
af63301
Update examples/color/colorbar_basics.py
Oct 2, 2020
762f61b
Update lib/matplotlib/tests/test_colorbar.py
Oct 2, 2020
682082a
Update lib/matplotlib/tests/test_colorbar.py
Oct 2, 2020
0548c97
Update lib/matplotlib/tests/test_colorbar.py
Oct 2, 2020
003ecf6
Update lib/matplotlib/tests/test_colorbar.py
Oct 2, 2020
7e0207c
Update lib/matplotlib/tests/test_colorbar.py
Oct 2, 2020
6e117ff
rename wh_ratios to height_ratios/width_ratios
Oct 10, 2020
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3 changes: 2 additions & 1 deletion 3 examples/color/colorbar_basics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -32,8 +32,9 @@
fig.colorbar(pos, ax=ax1)

# repeat everything above for the negative data
# you can specify location, anchor and shrink the colorbar
neg = ax2.imshow(Zneg, cmap='Reds_r', interpolation='none')
fig.colorbar(neg, ax=ax2)
fig.colorbar(neg, ax=ax2, location='right', anchor=(0, 0.3), shrink=0.7)

# Plot both positive and negative values between +/- 1.2
pos_neg_clipped = ax3.imshow(Z, cmap='RdBu', vmin=-1.2, vmax=1.2,
Expand Down
70 changes: 43 additions & 27 deletions 70 lib/matplotlib/colorbar.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1509,35 +1509,51 @@ def make_axes_gridspec(parent, *, location=None, orientation=None,
kw['orientation'] = loc_settings['orientation']
location = kw['ticklocation'] = loc_settings['location']

pad = loc_settings["pad"]
anchor = kw.pop('anchor', loc_settings['anchor'])
panchor = kw.pop('panchor', loc_settings['panchor'])
pad = kw.pop('pad', loc_settings["pad"])
wh_space = 2 * pad / (1 - pad)

# for shrinking
pad_s = (1 - shrink) * 0.5
wh_ratios = [pad_s, shrink, pad_s]

if location == "left":
gs = parent.get_subplotspec().subgridspec(
1, 2, wspace=wh_space, width_ratios=[fraction, 1-fraction-pad])
ss_main = gs[1]
ss_cb = gs[0].subgridspec(3, 1, hspace=0, height_ratios=wh_ratios)[1]
elif location == "right":
gs = parent.get_subplotspec().subgridspec(
1, 2, wspace=wh_space, width_ratios=[1-fraction-pad, fraction])
ss_main = gs[0]
ss_cb = gs[1].subgridspec(3, 1, hspace=0, height_ratios=wh_ratios)[1]
elif location == "top":
gs = parent.get_subplotspec().subgridspec(
2, 1, hspace=wh_space, height_ratios=[fraction, 1-fraction-pad])
ss_main = gs[1]
ss_cb = gs[0].subgridspec(1, 3, wspace=0, width_ratios=wh_ratios)[1]
aspect = 1 / aspect
else: # "bottom"
gs = parent.get_subplotspec().subgridspec(
2, 1, hspace=wh_space, height_ratios=[1-fraction-pad, fraction])
ss_main = gs[0]
ss_cb = gs[1].subgridspec(1, 3, wspace=0, width_ratios=wh_ratios)[1]
aspect = 1 / aspect
if location in ('left', 'right'):
# for shrinking
height_ratios = [
(1-anchor[1])*(1-shrink), shrink, anchor[1]*(1-shrink)]

if location == 'left':
gs = parent.get_subplotspec().subgridspec(
1, 2, wspace=wh_space,
width_ratios=[fraction, 1-fraction-pad])
ss_main = gs[1]
ss_cb = gs[0].subgridspec(
3, 1, hspace=0, height_ratios=height_ratios)[1]
else:
gs = parent.get_subplotspec().subgridspec(
1, 2, wspace=wh_space,
width_ratios=[1-fraction-pad, fraction])
ss_main = gs[0]
ss_cb = gs[1].subgridspec(
3, 1, hspace=0, height_ratios=height_ratios)[1]
else:
# for shrinking
width_ratios = [
anchor[0]*(1-shrink), shrink, (1-anchor[0])*(1-shrink)]

if location == 'bottom':
gs = parent.get_subplotspec().subgridspec(
2, 1, hspace=wh_space,
height_ratios=[1-fraction-pad, fraction])
ss_main = gs[0]
ss_cb = gs[1].subgridspec(
1, 3, wspace=0, width_ratios=width_ratios)[1]
aspect = 1 / aspect
else:
gs = parent.get_subplotspec().subgridspec(
2, 1, hspace=wh_space,
height_ratios=[fraction, 1-fraction-pad])
ss_main = gs[1]
ss_cb = gs[0].subgridspec(
1, 3, wspace=0, width_ratios=width_ratios)[1]
aspect = 1 / aspect

parent.set_subplotspec(ss_main)
parent.set_anchor(loc_settings["panchor"])
Expand Down
82 changes: 82 additions & 0 deletions 82 lib/matplotlib/tests/test_colorbar.py
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Expand Up @@ -622,3 +622,85 @@ def test_colorbar_int(clim):
im = ax.imshow([[*map(np.int16, clim)]])
fig.colorbar(im)
assert (im.norm.vmin, im.norm.vmax) == clim


def test_anchored_cbar_position_using_specgrid():
data = np.arange(1200).reshape(30, 40)
levels = [0, 200, 400, 600, 800, 1000, 1200]
shrink = 0.5
anchor_y = 0.3
# right
fig, ax = plt.subplots()
cs = ax.contourf(data, levels=levels)
cbar = plt.colorbar(
cs, ax=ax, use_gridspec=True,
location='right', anchor=(1, anchor_y), shrink=shrink)

# the bottom left corner of one ax is (x0, y0)
# the top right corner of one ax is (x1, y1)
# p0: the vertical / horizontal position of anchor
x0, y0, x1, y1 = ax.get_position().extents
cx0, cy0, cx1, cy1 = cbar.ax.get_position().extents
p0 = (y1 - y0) * anchor_y + y0

np.testing.assert_allclose(
[cy1, cy0],
[y1 * shrink + (1 - shrink) * p0, p0 * (1 - shrink) + y0 * shrink])
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I'm not sure I understand why the anchor point p0 should be affected by shrink.

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p0 is not affected by shrink, cy1 is the top of colorbar axes, which can be calculated using p0 and shrink
cy1 = y1 * shrink + (1 - shrink) * p0
while p0 and shrink do not affect each other

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I'm not saying they affect each other; I'm saying that shrink has an effect on p0 for cy0/cy1, and I don't know why. If p0 is an anchor, then it should not get shrunk.

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I looked at this again, and anchor is the anchor point of the colorbar, while I was thinking it was the anchor on the parent Axes, but that's defined by panchor. So this is why I was confused by this calculation.

However, that means that p0 doesn't seem to be calculated right, as it is calculating an anchor position in the parent Axes space (using y0/y1), but using anchor_y, which was used for the colorbar anchor position.

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In the test function, I will take location=right as an example

demo

the x0 y0 x1 y1 for the plot axes is [0.125, 0.11, 0.745, 0.88] (rounded to 2 digits) , blue region
the cx0 cy0 cx1 cy1 for cbar is [0.78, 0.22, 0.80, 0.61] , orange region

the p0 is the absolute y postion (red dot) of colorbar anchor against the plot, while anchor-y is a relative colorbar postion against the parent axes,
thus p0-y0 = (y1-y0) * anchor_y.

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I assumed the y value for colorbar anchor is the relative postion against the plot, not the absolute y position. Correct me if I am wrong.

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@ShawnChen1996 I think what would be convincing would be an example that shows clearly this version does close to the same as the version with use_gridspec=False, just to make sure the semantics are the same for anchor and panchor. For completeness it would be good if the were tested at more than one anchor along all four sides.

I know below we suggested not making an image test, but it would be helpful to see what the image looks like, even if it doesn't make it into the test. I guess in situations like this, I actually lean towards adding an image test since its hard to tell by looking at the numbers if things are working. But at least for review, it would be super helpful to see the image.

If the kwargs are being used the same as the old meaning of the kwargs, then we still have a documentation issue, but that shouldn't block this PR.


# left
fig, ax = plt.subplots()
cs = ax.contourf(data, levels=levels)
cbar = plt.colorbar(
cs, ax=ax, use_gridspec=True,
location='left', anchor=(1, anchor_y), shrink=shrink)

# the bottom left corner of one ax is (x0, y0)
# the top right corner of one ax is (x1, y1)
# p0: the vertical / horizontal position of anchor
x0, y0, x1, y1 = ax.get_position().extents
cx0, cy0, cx1, cy1 = cbar.ax.get_position().extents
p0 = (y1 - y0) * anchor_y + y0

np.testing.assert_allclose(
[cy1, cy0],
[y1 * shrink + (1 - shrink) * p0, p0 * (1 - shrink) + y0 * shrink])

# top
shawnchenx6 marked this conversation as resolved.
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shrink = 0.5
anchor_x = 0.3
fig, ax = plt.subplots()
cs = ax.contourf(data, levels=levels)
cbar = plt.colorbar(
cs, ax=ax, use_gridspec=True,
location='top', anchor=(anchor_x, 1), shrink=shrink)

# the bottom left corner of one ax is (x0, y0)
# the top right corner of one ax is (x1, y1)
# p0: the vertical / horizontal position of anchor
x0, y0, x1, y1 = ax.get_position().extents
cx0, cy0, cx1, cy1 = cbar.ax.get_position().extents
p0 = (x1 - x0) * anchor_x + x0

np.testing.assert_allclose(
[cx1, cx0],
[x1 * shrink + (1 - shrink) * p0, p0 * (1 - shrink) + x0 * shrink])

# bottom
shrink = 0.5
anchor_x = 0.3
fig, ax = plt.subplots()
cs = ax.contourf(data, levels=levels)
cbar = plt.colorbar(
cs, ax=ax, use_gridspec=True,
location='bottom', anchor=(anchor_x, 1), shrink=shrink)

# the bottom left corner of one ax is (x0, y0)
# the top right corner of one ax is (x1, y1)
# p0: the vertical / horizontal position of anchor
x0, y0, x1, y1 = ax.get_position().extents
cx0, cy0, cx1, cy1 = cbar.ax.get_position().extents
p0 = (x1 - x0) * anchor_x + x0

np.testing.assert_allclose(
[cx1, cx0],
[x1 * shrink + (1 - shrink) * p0, p0 * (1 - shrink) + x0 * shrink])
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