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Implement extend color bar for contourf #8806

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Implement extend color bar for contourf #8806

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bc8e4cd
extending lognorm colorbar to contourf
Jun 26, 2017
105abcc
Update ticker.py
Jun 26, 2017
016a6b2
Update test_colorbar.py
Jun 26, 2017
9fa40cc
Update tempLocator in case ticker is not given
Jun 26, 2017
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17 changes: 11 additions & 6 deletions lib/matplotlib/contour.py
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
import matplotlib.texmanager as texmanager
import matplotlib.transforms as mtransforms
from matplotlib.cbook import mplDeprecation
from matplotlib.ticker import Locator, LogLocator

# Import needed for adding manual selection capability to clabel
from matplotlib.blocking_input import BlockingContourLabeler
Expand Down Expand Up @@ -831,9 +832,6 @@ def __init__(self, ax, *args, **kwargs):
self.logscale = True
if norm is None:
norm = colors.LogNorm()
if self.extend is not 'neither':
raise ValueError('extend kwarg does not work yet with log '
' scale')
else:
self.logscale = False

Expand Down Expand Up @@ -1213,10 +1211,17 @@ def _process_levels(self):
# (Colorbar needs this even for line contours.)
self._levels = list(self.levels)

tempLocator = Locator()
if self.logscale:
tempLocator = LogLocator()
if self.locator is not None:
tempLocator = self.locator
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Instead of using a temporary Locator and then requiring that all Locators have 3 new private methods, I think it would be better to keep everything within the ContourBase class. This will be more readable than using Locator private methods that modify one of their arguments. It will likely require fewer LOC as well.

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@ghost ghost Jun 28, 2017 •
edited by ghost
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@efiring Thank you for the input. I took sometimes to think it over more carefully, I will fix it your way.

if self.extend in ('both', 'min'):
self._levels.insert(0, min(self.levels[0], self.zmin) - 1)
lowerbound = min(self.levels[0], self.zmin)
tempLocator._decrease_lower_bound(self._levels, lowerbound)
if self.extend in ('both', 'max'):
self._levels.append(max(self.levels[-1], self.zmax) + 1)
upperbound = max(self.levels[-1], self.zmax)
tempLocator._increase_upper_bound(self._levels, upperbound)
self._levels = np.asarray(self._levels)

if not self.filled:
Expand All @@ -1228,7 +1233,7 @@ def _process_levels(self):
# ...except that extended layers must be outside the
# normed range:
if self.extend in ('both', 'min'):
self.layers[0] = -1e150
self.layers[0] = tempLocator._get_lower_extend_layer_value()
if self.extend in ('both', 'max'):
self.layers[-1] = 1e150

Expand Down
Binary file added ...lotlib/tests/baseline_images/test_colorbar/extended_cbar_with_contourf_both.png
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Binary file added ...plotlib/tests/baseline_images/test_colorbar/extended_cbar_with_contourf_max.png
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Binary file added ...plotlib/tests/baseline_images/test_colorbar/extended_cbar_with_contourf_min.png
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33 changes: 33 additions & 0 deletions lib/matplotlib/tests/test_colorbar.py
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Expand Up @@ -10,6 +10,8 @@
from matplotlib.colors import BoundaryNorm, LogNorm
from matplotlib.cm import get_cmap
from matplotlib.colorbar import ColorbarBase
from matplotlib import ticker, cm
from matplotlib.mlab import bivariate_normal


def _get_cmap_norms():
Expand Down Expand Up @@ -308,3 +310,34 @@ def test_colorbar_lognorm_extension():
cb = ColorbarBase(ax, norm=LogNorm(vmin=0.1, vmax=1000.0),
orientation='vertical', extend='both')
assert cb._values[0] >= 0.0


@image_comparison(baseline_images=['extended_cbar_with_contourf_min',
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Please condense the test down to a single image with 3 subplots, saving time and space.

'extended_cbar_with_contourf_max',
'extended_cbar_with_contourf_both'],
extensions=['png'])
def test_extended_colorbar_on_contourf():
np.random.seed(1)
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Not used.

N = 100
x = np.linspace(-3.0, 3.0, N)
y = np.linspace(-2.0, 2.0, N)
X, Y = np.meshgrid(x, y)
z = (bivariate_normal(X, Y, 0.1, 0.2, 1.0, 1.0)
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For the purpose of a test you can use a simpler pattern with far fewer points. For example, you could use

z = np.logspace(0.1, 10, 24).reshape((4, 6))

and omit the X and Y entirely.

+ 0.1 * bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0))
plt.figure()
plt.subplot(111)
plt.contourf(X, Y, z, cmap=cm.PuBu_r, locator=ticker.LogLocator(),
extend='min')
plt.colorbar()
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For condensing the example you can use fig, axs = plt.subplots(ncols=3) and then use Axes and Figure method calls.

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Thanks. Will fix this test up.


plt.figure()
plt.subplot(111)
plt.contourf(X, Y, z, cmap=cm.PuBu_r, locator=ticker.LogLocator(),
extend='max')
plt.colorbar()

plt.figure()
plt.subplot(111)
plt.contourf(X, Y, z, cmap=cm.PuBu_r, locator=ticker.LogLocator(),
extend='both')
plt.colorbar()
18 changes: 18 additions & 0 deletions lib/matplotlib/ticker.py
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Expand Up @@ -1480,6 +1480,15 @@ def zoom(self, direction):
step = 0.1 * interval * direction
self.axis.set_view_interval(vmin + step, vmax - step, ignore=True)

def _decrease_lower_bound(self, levels, lower_bound):
levels.insert(0, lower_bound - 1.0)

def _increase_upper_bound(self, levels, upper_bound):
levels.append(upper_bound + 1.0)

def _get_lower_extend_layer_value(self):
return -1e150

def refresh(self):
"""refresh internal information based on current lim"""
pass
Expand Down Expand Up @@ -2192,6 +2201,15 @@ def nonsingular(self, vmin, vmax):
vmax = decade_up(vmax, self._base)
return vmin, vmax

def _decrease_lower_bound(self, levels, lower_bound):
levels.insert(0, lower_bound / self._base)

def _increase_upper_bound(self, levels, upper_bound):
levels.append(upper_bound * self._base)

def _get_lower_extend_layer_value(self):
return np.nextafter(0, 1)


class SymmetricalLogLocator(Locator):
"""
Expand Down