Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

ENH: add shading='nearest' and 'auto' topcolormesh#16258

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to ourterms of service andprivacy statement. We’ll occasionally send you account related emails.

Already on GitHub?Sign in to your account

Merged
anntzer merged 1 commit intomatplotlib:masterfromjklymak:fixpcolor2
Feb 9, 2020
Merged
Show file tree
Hide file tree
Changes fromall commits
Commits
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
25 changes: 25 additions & 0 deletionsdoc/users/next_whats_new/2020-01-18-pcolorshadingoptions.rst
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,25 @@
Pcolor and Pcolormesh now accept shading='nearest' and 'auto'
-------------------------------------------------------------

Previously `.axes.Axes.pcolor` and `.axes.Axes.pcolormesh` handled
the situation where *x* and *y* have the same (respective) size as *C* by
dropping the last row and column of *C*, and *x* and *y* are regarded as the
edges of the remaining rows and columns in *C*. However, many users want
*x* and *y* centered on the rows and columns of *C*.

To accommodate this, ``shading='nearest'`` and ``shading='auto'`` are
new allowed strings for the ``shading`` kwarg. ``'nearest'`` will center the
color on *x* and *y* if *x* and *y* have the same dimensions as *C*
(otherwise an error will be thrown). ``shading='auto'`` will choose 'flat'
or 'nearest' based on the size of *X*, *Y*, *C*.

If ``shading='flat'`` then *X*, and *Y* should have dimensions one larger
than *C*. If *X* and *Y* have the same dimensions as *C*, then the previous
behavior is used and the last row and column of *C* are dropped, and a
DeprecationWarning is emitted.

Users can also specify this by the new :rc:`pcolor.shading` in their
``.matplotlibrc`` or via `.rcParams`.

See :doc:`pcolormesh </gallery/images_contours_and_fields/pcolormesh_grids>`
for examples.
132 changes: 132 additions & 0 deletionsexamples/images_contours_and_fields/pcolormesh_grids.py
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,132 @@
"""
============================
pcolormesh grids and shading
============================

`.axes.Axes.pcolormesh` and `~.axes.Axes.pcolor` have a few options for
how grids are laid out and the shading between the grid points.

Generally, if *Z* has shape *(M, N)* then the grid *X* and *Y* can be
specified with either shape *(M+1, N+1)* or *(M, N)*, depending on the
argument for the ``shading`` keyword argument. Note that below we specify
vectors *x* as either length N or N+1 and *y* as length M or M+1, and
`~.axes.Axes.pcolormesh` internally makes the mesh matrices *X* and *Y* from
the input vectors.

"""

import matplotlib
import matplotlib.pyplot as plt
import numpy as np

###############################################################################
# Flat Shading
# ------------
#
# The grid specification with the least assumptions is ``shading='flat'``
# and if the grid is one larger than the data in each dimesion, i.e. has shape
# *(M+1, N+1)*. In that case *X* and *Y* sepcify the corners of quadrilaterals
# that are colored with the values in *Z*. Here we specify the edges of the
# *(3, 5)* quadrilaterals with *X* and *Y* that are *(4, 6)*.

nrows = 3
ncols = 5
Z = np.arange(nrows * ncols).reshape(nrows, ncols)
x = np.arange(ncols + 1)
y = np.arange(nrows + 1)

fig, ax = plt.subplots()
ax.pcolormesh(x, y, Z, shading='flat', vmin=Z.min(), vmax=Z.max())


def _annotate(ax, x, y, title):
# this all gets repeated below:
X, Y = np.meshgrid(x, y)
ax.plot(X.flat, Y.flat, 'o', color='m')
ax.set_xlim(-0.7, 5.2)
ax.set_ylim(-0.7, 3.2)
ax.set_title(title)

_annotate(ax, x, y, "shading='flat'")


###############################################################################
# Flat Shading, same shape grid
# -----------------------------
#
# Often, however, data is provided where *X* and *Y* match the shape of *Z*.
# As of Matplotlib v3.3, ``shading='flat'`` is deprecated when this is the
# case, a warning is raised, and the last row and column of *Z* are dropped.
# This dropping of the last row and column is what Matplotlib did silently
# previous to v3.3, and is compatible with what Matlab does.

x = np.arange(ncols) # note *not* ncols + 1 as before
y = np.arange(nrows)
fig, ax = plt.subplots()
ax.pcolormesh(x, y, Z, shading='flat', vmin=Z.min(), vmax=Z.max())
_annotate(ax, x, y, "shading='flat': X, Y, C same shape")

###############################################################################
# Nearest Shading, same shape grid
# --------------------------------
#
# Usually, dropping a row and column of data is not what the user means when
# the make *X*, *Y* and *Z* all the same shape. For this case, Matplotlib
# allows ``shading='nearest'`` and centers the colored qudrilaterals on the
# grid points.
#
# If a grid that is not the correct shape is passed with ``shading='nearest'``
# an error is raised.

fig, ax = plt.subplots()
ax.pcolormesh(x, y, Z, shading='nearest', vmin=Z.min(), vmax=Z.max())
_annotate(ax, x, y, "shading='nearest'")

###############################################################################
# Auto Shading
# ------------
#
# Its possible that the user would like the code to automatically choose
# which to use, in which case ``shading='auto'`` will decide whether to
# use 'flat' or 'nearest' shading based on the shapes of *X*, *Y* and *Z*.

fig, axs = plt.subplots(2, 1, constrained_layout=True)
ax = axs[0]
x = np.arange(ncols)
y = np.arange(nrows)
ax.pcolormesh(x, y, Z, shading='auto', vmin=Z.min(), vmax=Z.max())
_annotate(ax, x, y, "shading='auto'; X, Y, Z: same shape (nearest)")

ax = axs[1]
x = np.arange(ncols + 1)
y = np.arange(nrows + 1)
ax.pcolormesh(x, y, Z, shading='auto', vmin=Z.min(), vmax=Z.max())
_annotate(ax, x, y, "shading='auto'; X, Y one larger than Z (flat)")

###############################################################################
# Gouraud Shading
# ---------------
#
# `Gouraud shading <https://en.wikipedia.org/wiki/Gouraud_shading>`_ can also
# be specified, where the colour in the quadrilaterals is linearly
# interpolated between the grid points. The shapes of *X*, *Y*, *Z* must
# be the same.

fig, ax = plt.subplots(constrained_layout=True)
x = np.arange(ncols)
y = np.arange(nrows)
ax.pcolormesh(x, y, Z, shading='gouraud', vmin=Z.min(), vmax=Z.max())
_annotate(ax, x, y, "shading='gouraud'; X, Y same shape as Z")

plt.show()
#############################################################################
#
# ------------
#
# References
# """"""""""
#
# The use of the following functions and methods is shown in this example:

matplotlib.axes.Axes.pcolormesh
matplotlib.pyplot.pcolormesh
67 changes: 64 additions & 3 deletionsexamples/images_contours_and_fields/pcolormesh_levels.py
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -3,9 +3,9 @@
pcolormesh
==========

Shows howtocombine Normalization and Colormap instances to draw "levels" in
`~.axes.Axes.pcolor`, `~.axes.Axes.pcolormesh` and`~.axes.Axes.imshow` type
plots in a similar way to the levels keyword argument to contour/contourf.
`.axes.Axes.pcolormesh` allows youtogenerate 2-D image-style plots. Note it
is faster than the similar`~.axes.Axes.pcolor`.

"""

import matplotlib
Expand All@@ -14,6 +14,67 @@
from matplotlib.ticker import MaxNLocator
import numpy as np

###############################################################################
# Basic pcolormesh
# ----------------
#
# We usually specify a pcolormesh by defining the edge of quadrilaterals and
# the value of the quadrilateral. Note that here *x* and *y* each have one
# extra element than Z in the respective dimension.

np.random.seed(19680801)
Z = np.random.rand(6, 10)
x = np.arange(-0.5, 10, 1) # len = 11
y = np.arange(4.5, 11, 1) # len = 7

fig, ax = plt.subplots()
ax.pcolormesh(x, y, Z)

###############################################################################
# Non-rectilinear pcolormesh
# --------------------------
#
# Note that we can also specify matrices for *X* and *Y* and have
# non-rectilinear quadrilaterals.

x = np.arange(-0.5, 10, 1) # len = 11
y = np.arange(4.5, 11, 1) # len = 7
X, Y = np.meshgrid(x, y)
X = X + 0.2 * Y # tilt the coordinates.
Y = Y + 0.3 * X

fig, ax = plt.subplots()
ax.pcolormesh(X, Y, Z)

###############################################################################
# Centered Coordinates
# ---------------------
#
# Often a user wants to pass *X* and *Y* with the same sizes as *Z* to
# `.axes.Axes.pcolormesh`. This is also allowed if ``shading='auto'`` is
# passed (default set by :rc:`pcolor.shading`). Pre Matplotlib 3.3,
# ``shading='flat'`` would drop the last column and row of *Z*; while that
# is still allowed for back compatibility purposes, a DeprecationWarning is
# raised.

x = np.arange(10) # len = 10
y = np.arange(6) # len = 6
X, Y = np.meshgrid(x, y)

fig, axs = plt.subplots(2, 1, sharex=True, sharey=True)
axs[0].pcolormesh(X, Y, Z, vmin=np.min(Z), vmax=np.max(Z), shading='auto')
axs[0].set_title("shading='auto' = 'nearest'")
axs[1].pcolormesh(X, Y, Z, vmin=np.min(Z), vmax=np.max(Z), shading='flat')
axs[1].set_title("shading='flat'")

###############################################################################
# Making levels using Norms
# -------------------------
#
# Shows how to combine Normalization and Colormap instances to draw
# "levels" in `.axes.Axes.pcolor`, `.axes.Axes.pcolormesh`
# and `.axes.Axes.imshow` type plots in a similar
# way to the levels keyword argument to contour/contourf.

# make these smaller to increase the resolution
dx, dy = 0.05, 0.05
Expand Down
Loading
[8]ページ先頭
©2009-2025 Movatter.jp