code: #!/usr/bin/env python
  """
  Illustrate the difference between corner_mask=False and corner_mask=True
  for masked contour plots.
  """
  import matplotlib.pyplot as plt
  import numpy as np
  
  # Data to plot.
  x, y = np.meshgrid(np.arange(7), np.arange(10))
  z = np.sin(0.5*x)*np.cos(0.52*y)
  
  # Mask various z values.
  mask = np.zeros_like(z, dtype=np.bool)
  mask[2, 3:5] = True
  mask[3:5, 4] = True
  mask[7, 2] = True
  mask[5, 0] = True
  mask[0, 6] = True
  z = np.ma.array(z, mask=mask)
  
  corner_masks = [False, True]
  for i, corner_mask in enumerate(corner_masks):
      plt.subplot(1, 2, i+1)
      cs = plt.contourf(x, y, z, corner_mask=corner_mask)
      plt.contour(cs, colors='k')
      plt.title('corner_mask = {0}'.format(corner_mask))
  
      # Plot grid.
      plt.grid(c='k', ls='-', alpha=0.3)
  
      # Indicate masked points with red circles.
      plt.plot(np.ma.array(x, mask=~mask), y, 'ro')
  
  plt.show()
   from __future__ import (absolute_import, division, print_function,
                          unicode_literals)
  
  import six
  
  import matplotlib
  
  import matplotlib.artist as martist
  from matplotlib.artist import allow_rasterization
  from matplotlib import docstring
  import matplotlib.transforms as mtransforms
  import matplotlib.lines as mlines
  import matplotlib.patches as mpatches
  import matplotlib.path as mpath
  import matplotlib.cbook as cbook
  import numpy as np
  import warnings
  
  rcParams = matplotlib.rcParams
  
  
  class Spine(mpatches.Patch):
      """an axis spine -- the line noting the data area boundaries
  
      Spines are the lines connecting the axis tick marks and noting the
      boundaries of the data area. They can be placed at arbitrary
      positions. See function:`~matplotlib.spines.Spine.set_position`
      for more information.
  
      The default position is ``('outward',0)``.
  
      Spines are subclasses of class:`~matplotlib.patches.Patch`, and
      inherit much of their behavior.
  
      Spines draw a line or a circle, depending if
      function:`~matplotlib.spines.Spine.set_patch_line` or
      function:`~matplotlib.spines.Spine.set_patch_circle` has been
      called. Line-like is the default.
  
      """
      def __str__(self):
          return "Spine"
  
      @docstring.dedent_interpd
      def __init__(self, axes, spine_type, path, **kwargs):
          """
          - *axes* : the Axes instance containing the spine
          - *spine_type* : a string specifying the spine type
          - *path* : the path instance used to draw the spine
  
          Valid kwargs are:
          %(Patch)s
          """
          super(Spine, self).__init__(**kwargs)
          self.axes = axes
          self.set_figure(self.axes.figure)
          self.spine_type = spine_type
          self.set_facecolor('none')
          self.set_edgecolor(rcParams['axes.edgecolor'])
          self.set_linewidth(rcParams['axes.linewidth'])
          self.set_capstyle('projecting')
          self.axis = None
  
          self.set_zorder(2.5)
          self.set_transform(self.axes.transData)  # default transform
  
          self._bounds = None  # default bounds
          self._smart_bounds = False
  
          # Defer initial position determination. (Not much support for
          # non-rectangular axes is currently implemented, and this lets
          # them pass through the spines machinery without errors.)
          self._position = None
          if not isinstance(path, matplotlib.path.Path):
              msg = "'path' must be an instance of 'matplotlib.path.Path'"
              raise ValueError(msg)
          self._path = path
  
          # To support drawing both linear and circular spines, this
          # class implements Patch behavior two ways. If
          # self._patch_type == 'line', behave like a mpatches.PathPatch
          # instance. If self._patch_type == 'circle', behave like a
          # mpatches.Ellipse instance.
          self._patch_type = 'line'
  
          # Behavior copied from mpatches.Ellipse:
          # Note: This cannot be calculated until this is added to an Axes
          self._patch_transform = mtransforms.IdentityTransform()
  
      def set_smart_bounds(self, value):
          """set the spine and associated axis to have smart bounds"""
          self._smart_bounds = value
  
          # also set the axis if possible
          if self.spine_type in ('left', 'right'):
              self.axes.yaxis.set_smart_bounds(value)
          elif self.spine_type in ('top', 'bottom'):
              self.axes.xaxis.set_smart_bounds(value)
  
      def get_smart_bounds(self):
          """get whether the spine has smart bounds"""
          return self._smart_bounds
  
      def set_patch_circle(self, center, radius):
          """set the spine to be circular"""
          self._patch_type = 'circle'
          self._center = center
          self._width = radius * 2
          self._height = radius * 2
          self._angle = 0
          # circle drawn on axes transform
          self.set_transform(self.axes.transAxes)
  
      def set_patch_line(self):
          """set the spine to be linear"""
          self._patch_type = 'line'
  
      # Behavior copied from mpatches.Ellipse:
      def _recompute_transform(self):
          """NOTE: This cannot be called until after this has been added
                   to an Axes, otherwise unit conversion will fail. This
                   maxes it very important to call the accessor method and
                   not directly access the transformation member variable.
          """
          assert self._patch_type == 'circle'
          center = (self.convert_xunits(self._center[0]),
                    self.convert_yunits(self._center[1]))
          width = self.convert_xunits(self._width)
          height = self.convert_yunits(self._height)
          self._patch_transform = mtransforms.Affine2D() \
              .scale(width * 0.5, height * 0.5) \
              .rotate_deg(self._angle) \
              .translate(*center)
  
      def get_patch_transform(self):
          if self._patch_type == 'circle':
              self._recompute_transform()
              return self._patch_transform
          else:
              return super(Spine, self).get_patch_transform()
  
      def get_path(self):
          return self._path
  
      def _ensure_position_is_set(self):
          if self._position is None:
              # default position
              self._position = ('outward', 0.0)  # in points
              self.set_position(self._position)
  
      def register_axis(self, axis):
          """register an axis
  
          An axis should be registered with its corresponding spine from
          the Axes instance. This allows the spine to clear any axis
          properties when needed.
          """
          self.axis = axis
          if self.axis is not None:
              self.axis.cla()
  
      def cla(self):
          """Clear the current spine"""
          self._position = None  # clear position
          if self.axis is not None:
              self.axis.cla()
  
      def is_frame_like(self):
          """return True if directly on axes frame
  
          This is useful for determining if a spine is the edge of an
          old style MPL plot. If so, this function will return True.
          """
          self._ensure_position_is_set()
          position = self._position
          if cbook.is_string_like(position):
              if position == 'center':
                  position = ('axes', 0.5)
              elif position == 'zero':
                  position = ('data', 0)
          if len(position) != 2:
              raise ValueError("position should be 2-tuple")
          position_type, amount = position
          if position_type == 'outward' and amount == 0:
              return True
          else:
              return False
  
      def _adjust_location(self):
          """automatically set spine bounds to the view interval"""
  
          if self.spine_type == 'circle':
              return
  
          if self._bounds is None:
              if self.spine_type in ('left', 'right'):
                  low, high = self.axes.viewLim.intervaly
              elif self.spine_type in ('top', 'bottom'):
                  low, high = self.axes.viewLim.intervalx
              else:
                  raise ValueError('unknown spine spine_type: %s' %
                                   self.spine_type)
  
              if self._smart_bounds:
                  # attempt to set bounds in sophisticated way
                  if low > high:
                      # handle inverted limits
                      low, high = high, low
  
                  viewlim_low = low
                  viewlim_high = high
  
                  del low, high
  
                  if self.spine_type in ('left', 'right'):
                      datalim_low, datalim_high = self.axes.dataLim.intervaly
                      ticks = self.axes.get_yticks()
                  elif self.spine_type in ('top', 'bottom'):
                      datalim_low, datalim_high = self.axes.dataLim.intervalx
                      ticks = self.axes.get_xticks()
                  # handle inverted limits
                  ticks = list(ticks)
                  ticks.sort()
                  ticks = np.array(ticks)
                  if datalim_low > datalim_high:
                      datalim_low, datalim_high = datalim_high, datalim_low
  
                  if datalim_low < viewlim_low:
                      # Data extends past view. Clip line to view.
                      low = viewlim_low
                  else:
                      # Data ends before view ends.
                      cond = (ticks <= datalim_low) & (ticks >= viewlim_low)
                      tickvals = ticks[cond]
                      if len(tickvals):
                          # A tick is less than or equal to lowest data point.
                          low = tickvals[-1]
                      else:
                          # No tick is available
                          low = datalim_low
                      low = max(low, viewlim_low)
  
                  if datalim_high > viewlim_high:
                      # Data extends past view. Clip line to view.
                      high = viewlim_high
                  else:
                      # Data ends before view ends.
                      cond = (ticks >= datalim_high) & (ticks <= viewlim_high)
                      tickvals = ticks[cond]
                      if len(tickvals):
                          # A tick is greater than or equal to highest data
                          # point.
                          high = tickvals[0]
                      else:
                          # No tick is available
                          high = datalim_high
                      high = min(high, viewlim_high)
  
          else:
              low, high = self._bounds
  
          v1 = self._path.vertices
          assert v1.shape == (2, 2), 'unexpected vertices shape'
          if self.spine_type in ['left', 'right']:
              v1[0, 1] = low
              v1[1, 1] = high
          elif self.spine_type in ['bottom', 'top']:
              v1[0, 0] = low
              v1[1, 0] = high
          else:
              raise ValueError('unable to set bounds for spine "%s"' %
                               self.spine_type)
  
      @allow_rasterization
      def draw(self, renderer):
          self._adjust_location()
          return super(Spine, self).draw(renderer)
  
      def _calc_offset_transform(self):
          """calculate the offset transform performed by the spine"""
          self._ensure_position_is_set()
          position = self._position
          if cbook.is_string_like(position):
              if position == 'center':
                  position = ('axes', 0.5)
              elif position == 'zero':
                  position = ('data', 0)
          assert len(position) == 2, "position should be 2-tuple"
          position_type, amount = position
          assert position_type in ('axes', 'outward', 'data')
          if position_type == 'outward':
              if amount == 0:
                  # short circuit commonest case
                  self._spine_transform = ('identity',
                                           mtransforms.IdentityTransform())
              elif self.spine_type in ['left', 'right', 'top', 'bottom']:
                  offset_vec = {'left': (-1, 0),
                                'right': (1, 0),
                                'bottom': (0, -1),
                                'top': (0, 1),
                                }[self.spine_type]
                  # calculate x and y offset in dots
                  offset_x = amount * offset_vec[0] / 72.0
                  offset_y = amount * offset_vec[1] / 72.0
                  self._spine_transform = ('post',
                                           mtransforms.ScaledTranslation(
                                               offset_x,
                                               offset_y,
                                               self.figure.dpi_scale_trans))
              else:
                  warnings.warn('unknown spine type "%s": no spine '
                                'offset performed' % self.spine_type)
                  self._spine_transform = ('identity',
                                           mtransforms.IdentityTransform())
          elif position_type == 'axes':
              if self.spine_type in ('left', 'right'):
                  self._spine_transform = ('pre',
                                           mtransforms.Affine2D.from_values(
                                               # keep y unchanged, fix x at
                                               # amount
                                               0, 0, 0, 1, amount, 0))
              elif self.spine_type in ('bottom', 'top'):
                  self._spine_transform = ('pre',
                                           mtransforms.Affine2D.from_values(
                                               # keep x unchanged, fix y at
                                               # amount
                                               1, 0, 0, 0, 0, amount))
              else:
                  warnings.warn('unknown spine type "%s": no spine '
                                'offset performed' % self.spine_type)
                  self._spine_transform = ('identity',
                                           mtransforms.IdentityTransform())
          elif position_type == 'data':
              if self.spine_type in ('right', 'top'):
                  # The right and top spines have a default position of 1 in
                  # axes coordinates.  When specifying the position in data
                  # coordinates, we need to calculate the position relative to 0.
                  amount -= 1
              if self.spine_type in ('left', 'right'):
                  self._spine_transform = ('data',
                                           mtransforms.Affine2D().translate(
                                               amount, 0))
              elif self.spine_type in ('bottom', 'top'):
                  self._spine_transform = ('data',
                                           mtransforms.Affine2D().translate(
                                               0, amount))
              else:
                  warnings.warn('unknown spine type "%s": no spine '
                                'offset performed' % self.spine_type)
                  self._spine_transform = ('identity',
                                           mtransforms.IdentityTransform())
  
      def set_position(self, position):
          """set the position of the spine
  
          Spine position is specified by a 2 tuple of (position type,
          amount). The position types are:
  
          * 'outward' : place the spine out from the data area by the
            specified number of points. (Negative values specify placing the
            spine inward.)
  
          * 'axes' : place the spine at the specified Axes coordinate (from
            0.0-1.0).
  
          * 'data' : place the spine at the specified data coordinate.
  
          Additionally, shorthand notations define a special positions:
  
          * 'center' -> ('axes',0.5)
          * 'zero' -> ('data', 0.0)
  
          """
          if position in ('center', 'zero'):
              # special positions
              pass
          else:
              if len(position) != 2:
                  raise ValueError("position should be 'center' or 2-tuple")
              if position[0] not in ['outward', 'axes', 'data']:
                  msg = ("position[0] should be in [ 'outward' | 'axes' |"
                         " 'data' ]")
                  raise ValueError(msg)
          self._position = position
          self._calc_offset_transform()
  
          self.set_transform(self.get_spine_transform())
  
          if self.axis is not None:
              self.axis.reset_ticks()
  
      def get_position(self):
          """get the spine position"""
          self._ensure_position_is_set()
          return self._position
  
      def get_spine_transform(self):
          """get the spine transform"""
          self._ensure_position_is_set()
          what, how = self._spine_transform
  
          if what == 'data':
              # special case data based spine locations
              data_xform = self.axes.transScale + \
                  (how + self.axes.transLimits + self.axes.transAxes)
              if self.spine_type in ['left', 'right']:
                  result = mtransforms.blended_transform_factory(
                      data_xform, self.axes.transData)
              elif self.spine_type in ['top', 'bottom']:
                  result = mtransforms.blended_transform_factory(
                      self.axes.transData, data_xform)
              else:
                  raise ValueError('unknown spine spine_type: %s' %
                                   self.spine_type)
              return result
  
          if self.spine_type in ['left', 'right']:
              base_transform = self.axes.get_yaxis_transform(which='grid')
          elif self.spine_type in ['top', 'bottom']:
              base_transform = self.axes.get_xaxis_transform(which='grid')
          else:
              raise ValueError('unknown spine spine_type: %s' %
                               self.spine_type)
  
          if what == 'identity':
              return base_transform
          elif what == 'post':
              return base_transform + how
          elif what == 'pre':
              return how + base_transform
          else:
              raise ValueError("unknown spine_transform type: %s" % what)
  
      def set_bounds(self, low, high):
          """Set the bounds of the spine."""
          if self.spine_type == 'circle':
              raise ValueError(
                  'set_bounds() method incompatible with circular spines')
          self._bounds = (low, high)
  
      def get_bounds(self):
          """Get the bounds of the spine."""
          return self._bounds
  
      @classmethod
      def linear_spine(cls, axes, spine_type, **kwargs):
          """
          (staticmethod) Returns a linear :class:`Spine`.
          """
          # all values of 13 get replaced upon call to set_bounds()
          if spine_type == 'left':
              path = mpath.Path([(0.0, 13), (0.0, 13)])
          elif spine_type == 'right':
              path = mpath.Path([(1.0, 13), (1.0, 13)])
          elif spine_type == 'bottom':
              path = mpath.Path([(13, 0.0), (13, 0.0)])
          elif spine_type == 'top':
              path = mpath.Path([(13, 1.0), (13, 1.0)])
          else:
              raise ValueError('unable to make path for spine "%s"' % spine_type)
          result = cls(axes, spine_type, path, **kwargs)
          return result
  
      @classmethod
      def circular_spine(cls, axes, center, radius, **kwargs):
          """
          (staticmethod) Returns a circular :class:`Spine`.
          """
          path = mpath.Path.unit_circle()
          spine_type = 'circle'
          result = cls(axes, spine_type, path, **kwargs)
          result.set_patch_circle(center, radius)
          return result
  
      def set_color(self, c):
          """
          Set the edgecolor.
  
          ACCEPTS: matplotlib color arg or sequence of rgba tuples
  
          .. seealso::
  
              :meth:`set_facecolor`, :meth:`set_edgecolor`
                 For setting the edge or face color individually.
          """
          # The facecolor of a spine is always 'none' by default -- let
          # the user change it manually if desired.
          self.set_edgecolor(c)
  
apis: numpy.zeros_like matplotlib.pyplot.grid numpy.cos numpy.ma.array numpy.arange matplotlib.pyplot.subplot matplotlib.pyplot.show matplotlib.pyplot.contour numpy.sin matplotlib.pyplot.contourf
apis: matplotlib.cbook.is_string_like matplotlib.transforms.Affine2D matplotlib.transforms.IdentityTransform matplotlib.transforms.ScaledTranslation matplotlib.path.Path matplotlib.path.Path.unit_circle numpy.array matplotlib.transforms.blended_transform_factory matplotlib.transforms.Affine2D.from_values