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DOC: Add a plot to margins() to visualize the effect #28808

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merged 2 commits into from
Sep 13, 2024
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DOC: Add a plot to margins() to visualize the effect #28808

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DOC: Add a plot to margins() to visualize the effect
timhoffm Sep 12, 2024
8ea86fe
DOC: Add a plot to margins() to visualize the effect
timhoffm Sep 12, 2024
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42 changes: 42 additions & 0 deletions doc/_embedded_plots/axes_margins.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots(figsize=(6.5, 4))
x = np.linspace(0, 1, 33)
y = -np.sin(x * 2*np.pi)
ax.plot(x, y, 'o')
ax.margins(0.5, 0.2)
ax.set_title("margins(x=0.5, y=0.2)")

# fix the Axes limits so that the following helper drawings
# cannot change them further.
ax.set(xlim=ax.get_xlim(), ylim=ax.get_ylim())


def arrow(p1, p2, **props):
ax.annotate("", p1, p2,
arrowprops=dict(arrowstyle="<->", shrinkA=0, shrinkB=0, **props))


axmin, axmax = ax.get_xlim()
aymin, aymax = ax.get_ylim()
xmin, xmax = x.min(), x.max()
ymin, ymax = y.min(), y.max()

y0 = -0.8
ax.axvspan(axmin, xmin, color=("orange", 0.1))
ax.axvspan(xmax, axmax, color=("orange", 0.1))
arrow((xmin, y0), (xmax, y0), color="sienna")
arrow((xmax, y0), (axmax, y0), color="orange")
ax.text((xmax + axmax)/2, y0+0.05, "x margin\n* x data range",
ha="center", va="bottom", color="orange")
ax.text(0.55, y0+0.1, "x data range", va="bottom", color="sienna")

x0 = 0.1
ax.axhspan(aymin, ymin, color=("tab:green", 0.1))
ax.axhspan(ymax, aymax, color=("tab:green", 0.1))
arrow((x0, ymin), (x0, ymax), color="darkgreen")
arrow((x0, ymax), (x0, aymax), color="tab:green")
ax.text(x0, (ymax + aymax) / 2, " y margin * y data range",
va="center", color="tab:green")
ax.text(x0, 0.5, " y data range", color="darkgreen")
33 changes: 20 additions & 13 deletions lib/matplotlib/axes/_base.py
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Expand Up @@ -2736,19 +2736,22 @@ def set_ymargin(self, m):

def margins(self, *margins, x=None, y=None, tight=True):
"""
Set or retrieve autoscaling margins.
Set or retrieve margins around the data for autoscaling axis limits.

The padding added to each limit of the Axes is the *margin*
times the data interval. All input parameters must be floats
greater than -0.5. Passing both positional and keyword
arguments is invalid and will raise a TypeError. If no
arguments (positional or otherwise) are provided, the current
This allows to configure the padding around the data without having to
set explicit limits using `~.Axes.set_xlim` / `~.Axes.set_ylim`.

Autoscaling determines the axis limits by adding *margin* times the
data interval as padding around the data. See the following illustration:

.. plot:: _embedded_plots/axes_margins.py

All input parameters must be floats greater than -0.5. Passing both
positional and keyword arguments is invalid and will raise a TypeError.
If no arguments (positional or otherwise) are provided, the current
margins will remain unchanged and simply be returned.

Specifying any margin changes only the autoscaling; for example,
if *xmargin* is not None, then *xmargin* times the X data
interval will be added to each end of that interval before
it is used in autoscaling.
The default margins are :rc:`axes.xmargin` and :rc:`axes.ymargin`.

Parameters
----------
Expand Down Expand Up @@ -2780,10 +2783,14 @@ def margins(self, *margins, x=None, y=None, tight=True):
Notes
-----
If a previously used Axes method such as :meth:`pcolor` has set
:attr:`use_sticky_edges` to `True`, only the limits not set by
the "sticky artists" will be modified. To force all of the
margins to be set, set :attr:`use_sticky_edges` to `False`
`~.Axes.use_sticky_edges` to `True`, only the limits not set by
the "sticky artists" will be modified. To force all
margins to be set, set `~.Axes.use_sticky_edges` to `False`
before calling :meth:`margins`.

See Also
--------
.Axes.set_xmargin, .Axes.set_ymargin
"""

if margins and (x is not None or y is not None):
Expand Down
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