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Commit 73f2933

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sarantisaranti
committed
add legend to boxplot
1 parent 4ebc8ce commit 73f2933
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‎doc/users/next_whats_new/boxplot_legend_support.rst

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+60Lines changed: 60 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,60 @@
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Legend support for Boxplot
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Boxplots now support a *label* parameter to create legend entries.
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Legend labels can be passed as a list of strings to label multiple boxes in a single
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boxplot call:
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.. plot::
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:include-source: true
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:alt: Example of creating 3 boxplots and assigning legend labels as a sequence.
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import matplotlib.pyplot as plt
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import numpy as np
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np.random.seed(19680801)
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fruit_weights = [
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np.random.normal(130, 10, size=100),
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np.random.normal(125, 20, size=100),
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np.random.normal(120, 30, size=100),
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]
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labels = ['peaches', 'oranges', 'tomatoes']
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colors = ['peachpuff', 'orange', 'tomato']
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fig, ax = plt.subplots()
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ax.set_ylabel('fruit weight (g)')
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bplot = ax.boxplot(fruit_weights,
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patch_artist=True, # fill with color
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label=labels)
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# fill with colors
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for patch, color in zip(bplot['boxes'], colors):
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patch.set_facecolor(color)
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ax.set_xticks([])
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ax.legend()
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Or as a single string to each individual boxplot:
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.. plot::
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:include-source: true
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:alt: Example of creating 2 boxplots and assigning each legend label as a string.
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import matplotlib.pyplot as plt
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import numpy as np
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fig, ax = plt.subplots()
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data_A = np.random.random((100, 3))
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data_B = np.random.random((100, 3)) + 0.2
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pos = np.arange(3)
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ax.boxplot(data_A, positions=pos - 0.2, patch_artist=True, label='Box A',
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boxprops={'facecolor': 'steelblue'})
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ax.boxplot(data_B, positions=pos + 0.2, patch_artist=True, label='Box B',
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boxprops={'facecolor': 'lightblue'})
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ax.legend()

‎lib/matplotlib/axes/_axes.py

Copy file name to clipboardExpand all lines: lib/matplotlib/axes/_axes.py
+41-4Lines changed: 41 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -3797,7 +3797,7 @@ def boxplot(self, x, notch=None, sym=None, vert=None, whis=None,
37973797
labels=None, flierprops=None, medianprops=None,
37983798
meanprops=None, capprops=None, whiskerprops=None,
37993799
manage_ticks=True, autorange=False, zorder=None,
3800-
capwidths=None):
3800+
capwidths=None, label=None):
38013801
"""
38023802
Draw a box and whisker plot.
38033803
@@ -3978,6 +3978,18 @@ def boxplot(self, x, notch=None, sym=None, vert=None, whis=None,
39783978
The style of the median.
39793979
meanprops : dict, default: None
39803980
The style of the mean.
3981+
label : str or list of str, optional
3982+
Legend labels. Use a single string when all boxes have the same style and
3983+
you only want a single legend entry for them. Use a list of strings to
3984+
label all boxes individually. To be distinguishable, the boxes should be
3985+
styled individually, which is currently only possible by modifying the
3986+
returned artists, see e.g. :doc:`/gallery/statistics/boxplot_demo`.
3987+
3988+
In the case of a single string, the legend entry will technically be
3989+
associated with the first box only. By default, the legend will show the
3990+
median line (``result["medians"]``); if *patch_artist* is True, the legend
3991+
will show the box `Patch` artists (``result["boxes"]``) instead.
3992+
39813993
data : indexable object, optional
39823994
DATA_PARAMETER_PLACEHOLDER
39833995
@@ -4098,7 +4110,7 @@ def boxplot(self, x, notch=None, sym=None, vert=None, whis=None,
40984110
meanline=meanline, showfliers=showfliers,
40994111
capprops=capprops, whiskerprops=whiskerprops,
41004112
manage_ticks=manage_ticks, zorder=zorder,
4101-
capwidths=capwidths)
4113+
capwidths=capwidths, label=label)
41024114
return artists
41034115

41044116
def bxp(self, bxpstats, positions=None, widths=None, vert=True,
@@ -4107,7 +4119,7 @@ def bxp(self, bxpstats, positions=None, widths=None, vert=True,
41074119
boxprops=None, whiskerprops=None, flierprops=None,
41084120
medianprops=None, capprops=None, meanprops=None,
41094121
meanline=False, manage_ticks=True, zorder=None,
4110-
capwidths=None):
4122+
capwidths=None, label=None):
41114123
"""
41124124
Draw a box and whisker plot from pre-computed statistics.
41134125
@@ -4190,6 +4202,18 @@ def bxp(self, bxpstats, positions=None, widths=None, vert=True,
41904202
If True, the tick locations and labels will be adjusted to match the
41914203
boxplot positions.
41924204
4205+
label : str or list of str, optional
4206+
Legend labels. Use a single string when all boxes have the same style and
4207+
you only want a single legend entry for them. Use a list of strings to
4208+
label all boxes individually. To be distinguishable, the boxes should be
4209+
styled individually, which is currently only possible by modifying the
4210+
returned artists, see e.g. :doc:`/gallery/statistics/boxplot_demo`.
4211+
4212+
In the case of a single string, the legend entry will technically be
4213+
associated with the first box only. By default, the legend will show the
4214+
median line (``result["medians"]``); if *patch_artist* is True, the legend
4215+
will show the box `Patch` artists (``result["boxes"]``) instead.
4216+
41934217
zorder : float, default: ``Line2D.zorder = 2``
41944218
The zorder of the resulting boxplot.
41954219
@@ -4354,6 +4378,7 @@ def do_patch(xs, ys, **kwargs):
43544378
if showbox:
43554379
do_box = do_patch if patch_artist else do_plot
43564380
boxes.append(do_box(box_x, box_y, **box_kw))
4381+
median_kw.setdefault('label', '_nolegend_')
43574382
# draw the whiskers
43584383
whisker_kw.setdefault('label', '_nolegend_')
43594384
whiskers.append(do_plot(whis_x, whislo_y, **whisker_kw))
@@ -4364,7 +4389,6 @@ def do_patch(xs, ys, **kwargs):
43644389
caps.append(do_plot(cap_x, cap_lo, **cap_kw))
43654390
caps.append(do_plot(cap_x, cap_hi, **cap_kw))
43664391
# draw the medians
4367-
median_kw.setdefault('label', '_nolegend_')
43684392
medians.append(do_plot(med_x, med_y, **median_kw))
43694393
# maybe draw the means
43704394
if showmeans:
@@ -4382,6 +4406,19 @@ def do_patch(xs, ys, **kwargs):
43824406
flier_y = stats['fliers']
43834407
fliers.append(do_plot(flier_x, flier_y, **flier_kw))
43844408

4409+
# Set legend labels
4410+
if label:
4411+
box_or_med = boxes if showbox and patch_artist else medians
4412+
if cbook.is_scalar_or_string(label):
4413+
# assign the label only to the first box
4414+
box_or_med[0].set_label(label)
4415+
else: # label is a sequence
4416+
if len(box_or_med) != len(label):
4417+
raise ValueError("There must be an equal number of legend"
4418+
" labels and boxplots.")
4419+
for artist, lbl in zip(box_or_med, label):
4420+
artist.set_label(lbl)
4421+
43854422
if manage_ticks:
43864423
axis_name = "x" if vert else "y"
43874424
interval = getattr(self.dataLim, f"interval{axis_name}")

‎lib/matplotlib/axes/_axes.pyi

Copy file name to clipboardExpand all lines: lib/matplotlib/axes/_axes.pyi
+2Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -372,6 +372,7 @@ class Axes(_AxesBase):
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autorange: bool = ...,
373373
zorder: float | None = ...,
374374
capwidths: float | ArrayLike | None = ...,
375+
label: Sequence[str] | None = ...,
375376
*,
376377
data=...,
377378
) -> dict[str, Any]: ...
@@ -397,6 +398,7 @@ class Axes(_AxesBase):
397398
manage_ticks: bool = ...,
398399
zorder: float | None = ...,
399400
capwidths: float | ArrayLike | None = ...,
401+
label: Sequence[str] | None = ...,
400402
) -> dict[str, Any]: ...
401403
def scatter(
402404
self,

‎lib/matplotlib/pyplot.py

Copy file name to clipboardExpand all lines: lib/matplotlib/pyplot.py
+2Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2865,6 +2865,7 @@ def boxplot(
28652865
autorange: bool = False,
28662866
zorder: float | None = None,
28672867
capwidths: float | ArrayLike | None = None,
2868+
label: Sequence[str] | None = None,
28682869
*,
28692870
data=None,
28702871
) -> dict[str, Any]:
@@ -2896,6 +2897,7 @@ def boxplot(
28962897
autorange=autorange,
28972898
zorder=zorder,
28982899
capwidths=capwidths,
2900+
label=label,
28992901
**({"data": data} if data is not None else {}),
29002902
)
29012903

‎lib/matplotlib/tests/test_legend.py

Copy file name to clipboardExpand all lines: lib/matplotlib/tests/test_legend.py
+32Lines changed: 32 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1450,3 +1450,35 @@ def test_boxplot_labels():
14501450
handles, labels = ax.get_legend_handles_labels()
14511451
assert len(handles) == 0
14521452
assert len(labels) == 0
1453+
1454+
1455+
def test_boxplot_legend_labels():
1456+
# Test that legend entries are generated when passing `label`.
1457+
np.random.seed(19680801)
1458+
data = np.random.random((10, 4))
1459+
fig, axs = plt.subplots(nrows=1, ncols=4)
1460+
legend_labels = ['box A', 'box B', 'box C', 'box D']
1461+
1462+
# Testing legend labels and patch passed to legend.
1463+
bp1 = axs[0].boxplot(data, patch_artist=True, label=legend_labels)
1464+
assert [v.get_label() for v in bp1['boxes']] == legend_labels
1465+
handles, labels = axs[0].get_legend_handles_labels()
1466+
assert labels == legend_labels
1467+
assert all(isinstance(h, mpl.patches.PathPatch) for h in handles)
1468+
1469+
# Testing legend without `box`.
1470+
bp2 = axs[1].boxplot(data, label=legend_labels, showbox=False)
1471+
# Without a box, The legend entries should be passed from the medians.
1472+
assert [v.get_label() for v in bp2['medians']] == legend_labels
1473+
handles, labels = axs[1].get_legend_handles_labels()
1474+
assert labels == legend_labels
1475+
assert all(isinstance(h, mpl.lines.Line2D) for h in handles)
1476+
1477+
# Testing legend with number of labels different from number of boxes.
1478+
with pytest.raises(ValueError, match='There must be an equal number'):
1479+
bp3 = axs[2].boxplot(data, label=legend_labels[:-1])
1480+
1481+
# Test that for a string label, only the first box gets a label.
1482+
bp4 = axs[3].boxplot(data, label='box A')
1483+
assert bp4['medians'][0].get_label() == 'box A'
1484+
assert all(x.get_label().startswith("_") for x in bp4['medians'][1:])

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