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Mar 22, 2018
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ENH: adjustable colorbar ticks #9903

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52e5d81
ENH: colorbar ticks adjustable to colorbar size
jklymak Mar 18, 2018
b74c0fd
FIX: add loglocator for minor colorbar
jklymak Mar 19, 2018
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8 changes: 8 additions & 0 deletions doc/api/api_changes/2017-12-01-JMK.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
The ticks for colorbar now adjust for the size of the colorbar
--------------------------------------------------------------

Colorbar ticks now adjust for the size of the colorbar if the
colorbar is made from a mappable that is not a contour or
doesn't have a BoundaryNorm, or boundaries are not specified.
If boundaries, etc are specified, the colorbar maintains the
original behaviour.
7 changes: 7 additions & 0 deletions doc/users/next_whats_new/colorbarticks.rst
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@@ -0,0 +1,7 @@
Colorbar ticks can now be automatic
-----------------------------------

The number of ticks on colorbars was appropriate for a large colorbar, but
looked bad if the colorbar was made smaller (i.e. via the ``shrink`` kwarg).
This has been changed so that the number of ticks is now responsive to how
large the colorbar is.
216 changes: 169 additions & 47 deletions lib/matplotlib/colorbar.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
import six
from six.moves import xrange, zip

import logging
import warnings

import numpy as np
Expand All @@ -44,6 +45,8 @@
import matplotlib._constrained_layout as constrained_layout
from matplotlib import docstring

_log = logging.getLogger(__name__)

make_axes_kw_doc = '''

============= ====================================================
Expand Down Expand Up @@ -217,6 +220,63 @@ def _set_ticks_on_axis_warn(*args, **kw):
warnings.warn("Use the colorbar set_ticks() method instead.")


class _ColorbarAutoLocator(ticker.MaxNLocator):
"""
AutoLocator for Colorbar

This locator is just a `.MaxNLocator` except the min and max are
clipped by the norm's min and max (i.e. vmin/vmax from the
image/pcolor/contour object). This is necessary so ticks don't
extrude into the "extend regions".
"""

def __init__(self, colorbar):
"""
This ticker needs to know the *colorbar* so that it can access
its *vmin* and *vmax*. Otherwise it is the same as
`~.ticker.AutoLocator`.
"""

self._colorbar = colorbar
nbins = 'auto'
steps = [1, 2, 2.5, 5, 10]
ticker.MaxNLocator.__init__(self, nbins=nbins, steps=steps)

def tick_values(self, vmin, vmax):
vmin = max(vmin, self._colorbar.norm.vmin)
vmax = min(vmax, self._colorbar.norm.vmax)
return ticker.MaxNLocator.tick_values(self, vmin, vmax)


class _ColorbarLogLocator(ticker.LogLocator):
"""
LogLocator for Colorbarbar

This locator is just a `.LogLocator` except the min and max are
clipped by the norm's min and max (i.e. vmin/vmax from the
image/pcolor/contour object). This is necessary so ticks don't
extrude into the "extend regions".

"""
def __init__(self, colorbar, *args, **kwargs):
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Same as above comment on __init__

"""
_ColorbarLogLocator(colorbar, *args, **kwargs)

This ticker needs to know the *colorbar* so that it can access
its *vmin* and *vmax*. Otherwise it is the same as
`~.ticker.LogLocator`. The ``*args`` and ``**kwargs`` are the
same as `~.ticker.LogLocator`.
"""
self._colorbar = colorbar
ticker.LogLocator.__init__(self, *args, **kwargs)

def tick_values(self, vmin, vmax):
vmin = self._colorbar.norm.vmin
vmax = self._colorbar.norm.vmax
ticks = ticker.LogLocator.tick_values(self, vmin, vmax)
return ticks[(ticks >= vmin) & (ticks <= vmax)]


class ColorbarBase(cm.ScalarMappable):
'''
Draw a colorbar in an existing axes.
Expand Down Expand Up @@ -346,8 +406,15 @@ def draw_all(self):
and do all the drawing.
'''

# sets self._boundaries and self._values in real data units.
# takes into account extend values:
self._process_values()
# sets self.vmin and vmax in data units, but just for
# the part of the colorbar that is not part of the extend
# patch:
self._find_range()
# returns the X and Y mesh, *but* this was/is in normalized
# units:
X, Y = self._mesh()
C = self._values[:, np.newaxis]
self._config_axes(X, Y)
Expand All @@ -356,35 +423,105 @@ def draw_all(self):

def config_axis(self):
ax = self.ax
if (isinstance(self.norm, colors.LogNorm)
and self._use_auto_colorbar_locator()):
# *both* axes are made log so that determining the
# mid point is easier.
ax.set_xscale('log')
ax.set_yscale('log')

if self.orientation == 'vertical':
ax.xaxis.set_ticks([])
# location is either one of 'bottom' or 'top'
ax.yaxis.set_label_position(self.ticklocation)
ax.yaxis.set_ticks_position(self.ticklocation)
long_axis, short_axis = ax.yaxis, ax.xaxis
else:
ax.yaxis.set_ticks([])
# location is either one of 'left' or 'right'
ax.xaxis.set_label_position(self.ticklocation)
ax.xaxis.set_ticks_position(self.ticklocation)
long_axis, short_axis = ax.xaxis, ax.yaxis

long_axis.set_label_position(self.ticklocation)
long_axis.set_ticks_position(self.ticklocation)
short_axis.set_ticks([])
short_axis.set_ticks([], minor=True)

self._set_label()

def _get_ticker_locator_formatter(self):
"""
This code looks at the norm being used by the colorbar
and decides what locator and formatter to use. If ``locator`` has
already been set by hand, it just returns
``self.locator, self.formatter``.
"""
locator = self.locator
formatter = self.formatter
if locator is None:
if self.boundaries is None:
if isinstance(self.norm, colors.NoNorm):
nv = len(self._values)
base = 1 + int(nv / 10)
locator = ticker.IndexLocator(base=base, offset=0)
elif isinstance(self.norm, colors.BoundaryNorm):
b = self.norm.boundaries
locator = ticker.FixedLocator(b, nbins=10)
elif isinstance(self.norm, colors.LogNorm):
locator = _ColorbarLogLocator(self)
elif isinstance(self.norm, colors.SymLogNorm):
# The subs setting here should be replaced
# by logic in the locator.
locator = ticker.SymmetricalLogLocator(
subs=np.arange(1, 10),
linthresh=self.norm.linthresh,
base=10)
else:
if mpl.rcParams['_internal.classic_mode']:
locator = ticker.MaxNLocator()
else:
locator = _ColorbarAutoLocator(self)
else:
b = self._boundaries[self._inside]
locator = ticker.FixedLocator(b, nbins=10)
_log.debug('locator: %r', locator)
return locator, formatter

def _use_auto_colorbar_locator(self):
"""
Return if we should use an adjustable tick locator or a fixed
one. (check is used twice so factored out here...)
"""
return (self.boundaries is None
and self.values is None
and ((type(self.norm) == colors.Normalize)
or (type(self.norm) == colors.LogNorm)))

def update_ticks(self):
"""
Force the update of the ticks and ticklabels. This must be
called whenever the tick locator and/or tick formatter changes.
"""
ax = self.ax
ticks, ticklabels, offset_string = self._ticker()
if self.orientation == 'vertical':
ax.yaxis.set_ticks(ticks)
ax.set_yticklabels(ticklabels)
ax.yaxis.get_major_formatter().set_offset_string(offset_string)
# get the locator and formatter. Defaults to
# self.locator if not None..
locator, formatter = self._get_ticker_locator_formatter()

if self.orientation == 'vertical':
long_axis, short_axis = ax.yaxis, ax.xaxis
else:
ax.xaxis.set_ticks(ticks)
ax.set_xticklabels(ticklabels)
ax.xaxis.get_major_formatter().set_offset_string(offset_string)
long_axis, short_axis = ax.xaxis, ax.yaxis

if self._use_auto_colorbar_locator():
_log.debug('Using auto colorbar locator on colorbar')
_log.debug('locator: %r', locator)
long_axis.set_major_locator(locator)
long_axis.set_major_formatter(formatter)
if type(self.norm) == colors.LogNorm:
long_axis.set_minor_locator(_ColorbarLogLocator(self,
base=10., subs='auto'))
long_axis.set_minor_formatter(
ticker.LogFormatter()
)
else:
_log.debug('Using fixed locator on colorbar')
ticks, ticklabels, offset_string = self._ticker(locator, formatter)
long_axis.set_ticks(ticks)
long_axis.set_ticklabels(ticklabels)
long_axis.get_major_formatter().set_offset_string(offset_string)

def set_ticks(self, ticks, update_ticks=True):
"""
Expand Down Expand Up @@ -520,6 +657,7 @@ def _add_solids(self, X, Y, C):
# since the axes object should already have hold set.
_hold = self.ax._hold
self.ax._hold = True
_log.debug('Setting pcolormesh')
col = self.ax.pcolormesh(*args, **kw)
self.ax._hold = _hold
#self.add_observer(col) # We should observe, not be observed...
Expand Down Expand Up @@ -573,39 +711,11 @@ def add_lines(self, levels, colors, linewidths, erase=True):
self.ax.add_collection(col)
self.stale = True

def _ticker(self):
def _ticker(self, locator, formatter):
'''
Return the sequence of ticks (colorbar data locations),
ticklabels (strings), and the corresponding offset string.
'''
locator = self.locator
formatter = self.formatter
if locator is None:
if self.boundaries is None:
if isinstance(self.norm, colors.NoNorm):
nv = len(self._values)
base = 1 + int(nv / 10)
locator = ticker.IndexLocator(base=base, offset=0)
elif isinstance(self.norm, colors.BoundaryNorm):
b = self.norm.boundaries
locator = ticker.FixedLocator(b, nbins=10)
elif isinstance(self.norm, colors.LogNorm):
locator = ticker.LogLocator(subs='all')
elif isinstance(self.norm, colors.SymLogNorm):
# The subs setting here should be replaced
# by logic in the locator.
locator = ticker.SymmetricalLogLocator(
subs=np.arange(1, 10),
linthresh=self.norm.linthresh,
base=10)
else:
if mpl.rcParams['_internal.classic_mode']:
locator = ticker.MaxNLocator()
else:
locator = ticker.AutoLocator()
else:
b = self._boundaries[self._inside]
locator = ticker.FixedLocator(b, nbins=10)
if isinstance(self.norm, colors.NoNorm) and self.boundaries is None:
intv = self._values[0], self._values[-1]
else:
Expand Down Expand Up @@ -845,17 +955,29 @@ def _mesh(self):
transposition for a horizontal colorbar are done outside
this function.
'''
# if boundaries and values are None, then we can go ahead and
# scale this up for Auto tick location. Otherwise we
# want to keep normalized between 0 and 1 and use manual tick
# locations.

x = np.array([0.0, 1.0])
if self.spacing == 'uniform':
y = self._uniform_y(self._central_N())
else:
y = self._proportional_y()
if self._use_auto_colorbar_locator():
y = self.norm.inverse(y)
x = self.norm.inverse(x)
self._y = y
X, Y = np.meshgrid(x, y)
if self._use_auto_colorbar_locator():
xmid = self.norm.inverse(0.5)
else:
xmid = 0.5
if self._extend_lower() and not self.extendrect:
X[0, :] = 0.5
X[0, :] = xmid
if self._extend_upper() and not self.extendrect:
X[-1, :] = 0.5
X[-1, :] = xmid
return X, Y

def _locate(self, x):
Expand Down
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