Example #1
0
 def _contour_args(self, filled, origin, extent, *args):
     if filled: fn = 'contourf'
     else:      fn = 'contour'
     Nargs = len(args)
     if Nargs <= 2:
         z = args[0]
         x, y = self._initialize_x_y(z, origin, extent)
     elif Nargs <=4:
         x,y,z = self._check_xyz(args[:3])
     else:
         raise TypeError("Too many arguments to %s; see help(%s)" % (fn,fn))
     z = ma.asarray(z)  # Convert to native masked array format if necessary.
     if Nargs == 1 or Nargs == 3:
         lev = self._autolev(z, 7, filled)
     else:   # 2 or 4 args
         level_arg = args[-1]
         if type(level_arg) == int:
             lev = self._autolev(z, level_arg, filled)
         elif iterable(level_arg) and len(shape(level_arg)) == 1:
             lev = array([float(fl) for fl in level_arg])
         else:
             raise TypeError("Last %s arg must give levels; see help(%s)" % (fn,fn))
     if filled and len(lev) < 2:
         raise ValueError("Filled contours require at least 2 levels.")
     self.ax.set_xlim((ma.minimum(x), ma.maximum(x)))
     self.ax.set_ylim((ma.minimum(y), ma.maximum(y)))
     # Workaround for cntr.c bug wrt masked interior regions:
     #if filled:
     #    z = ma.masked_array(z.filled(-1e38))
     # It's not clear this is any better than the original bug.
     return (x, y, z, lev)
Example #2
0
    def _contour_args(self, *args):
        if self.filled: fn = 'contourf'
        else:           fn = 'contour'
        Nargs = len(args)
        if Nargs <= 2:
            z = args[0]
            x, y = self._initialize_x_y(z)
        elif Nargs <=4:
            x,y,z = self._check_xyz(args[:3])
        else:
            raise TypeError("Too many arguments to %s; see help(%s)" % (fn,fn))
        z = ma.asarray(z)  # Convert to native masked array format if necessary.
        self.zmax = ma.maximum(z)
        self.zmin = ma.minimum(z)
        self._auto = False
        if self.levels is None:
            if Nargs == 1 or Nargs == 3:
                lev = self._autolev(z, 7)
            else:   # 2 or 4 args
                level_arg = args[-1]
                if type(level_arg) == int:
                    lev = self._autolev(z, level_arg)
                elif iterable(level_arg) and len(shape(level_arg)) == 1:
                    lev = array([float(fl) for fl in level_arg])
                else:
                    raise TypeError("Last %s arg must give levels; see help(%s)" % (fn,fn))
            if self.filled and len(lev) < 2:
                raise ValueError("Filled contours require at least 2 levels.")
            # Workaround for cntr.c bug wrt masked interior regions:
            #if filled:
            #    z = ma.masked_array(z.filled(-1e38))
            # It's not clear this is any better than the original bug.
            self.levels = lev
        #if self._auto and self.extend in ('both', 'min', 'max'):
        #    raise TypeError("Auto level selection is inconsistent "
        #                             + "with use of 'extend' kwarg")
        self._levels = list(self.levels)
        if self.extend in ('both', 'min'):
            self._levels.insert(0, self.zmin - 1)
        if self.extend in ('both', 'max'):
            self._levels.append(self.zmax + 1)
        self._levels = asarray(self._levels)
        self.vmin = amin(self.levels)  # alternative would be self.layers
        self.vmax = amax(self.levels)
        if self.extend in ('both', 'min') or self.clip_ends:
            self.vmin = 2 * self.levels[0] - self.levels[1]
        if self.extend in ('both', 'max') or self.clip_ends:
            self.vmax = 2 * self.levels[-1] - self.levels[-2]
        self.layers = self._levels # contour: a line is a thin layer
        if self.filled:
            self.layers = 0.5 * (self._levels[:-1] + self._levels[1:])
            if self.extend in ('both', 'min') or self.clip_ends:
                self.layers[0] = 0.5 * (self.vmin + self._levels[1])
            if self.extend in ('both', 'max') or self.clip_ends:
                self.layers[-1] = 0.5 * (self.vmax + self._levels[-2])

        return (x, y, z)
Example #3
0
    def _autolev(self, z, N):
        '''
        Select contour levels to span the data.

        We need two more levels for filled contours than for
        line contours, because for the latter we need to specify
        the lower and upper boundary of each range. For example,
        a single contour boundary, say at z = 0, requires only
        one contour line, but two filled regions, and therefore
        three levels to provide boundaries for both regions.
        '''
        zmax = ma.maximum(z)
        zmin = ma.minimum(z)
        zmargin = (zmax - zmin) * 0.001 # so z < (zmax + zmargin)
        if self.filled:
            lev = linspace(zmin, zmax + zmargin, N+2)
        else:
            lev = linspace(zmin, zmax + zmargin, N+2)[1:-1]
        return lev
Example #4
0
    def _autolev(self, z, N):
        '''
        Select contour levels to span the data.

        We need two more levels for filled contours than for
        line contours, because for the latter we need to specify
        the lower and upper boundary of each range. For example,
        a single contour boundary, say at z = 0, requires only
        one contour line, but two filled regions, and therefore
        three levels to provide boundaries for both regions.
        '''
        zmax = ma.maximum(z)
        zmin = ma.minimum(z)
        zmargin = (zmax - zmin) * 0.001 # so z < (zmax + zmargin)
        if self.filled:
            lev = linspace(zmin, zmax + zmargin, N+2)
        else:
            lev = linspace(zmin, zmax + zmargin, N+2)[1:-1]
        return lev
Example #5
0
    def _autolev(self, z, N, filled, badmask):
        '''
        Select contour levels to span the data.

        We need one more level for filled contours than for
        line contours, because for the latter we need to specify
        the lower and upper boundary of each range. For example,
        a single contour boundary, say at z = 0, requires only
        one contour line, but two filled regions, and therefore
        two levels.  These are taken as the lower boundaries of
        the regions.
        '''
        rz = ma.masked_array(z, badmask)
        zmax = ma.maximum(rz)  # was: zmax = amax(rz)
        zmin = ma.minimum(rz)
        if filled:
            lev = linspace(zmin, zmax, N + 2)[:-1]
        else:
            lev = linspace(zmin, zmax, N + 2)[1:-1]
        return lev
Example #6
0
    def _autolev(self, z, N, filled, badmask):
        '''
        Select contour levels to span the data.

        We need one more level for filled contours than for
        line contours, because for the latter we need to specify
        the lower and upper boundary of each range. For example,
        a single contour boundary, say at z = 0, requires only
        one contour line, but two filled regions, and therefore
        two levels.  These are taken as the lower boundaries of
        the regions.
        '''
        rz = ma.masked_array(z, badmask)
        zmax = ma.maximum(rz)     # was: zmax = amax(rz)
        zmin = ma.minimum(rz)
        if filled:
            lev = linspace(zmin, zmax, N+2)[:-1]
        else:
            lev = linspace(zmin, zmax, N+2)[1:-1]
        return lev
Example #7
0
    def _autolev(self, z, N):
        '''
        Select contour levels to span the data.

        We need two more levels for filled contours than for
        line contours, because for the latter we need to specify
        the lower and upper boundary of each range. For example,
        a single contour boundary, say at z = 0, requires only
        one contour line, but two filled regions, and therefore
        three levels to provide boundaries for both regions.
        '''
        zmax = ma.maximum(z)
        zmin = ma.minimum(z)
        zmargin = (zmax - zmin) * 0.001 # so z < (zmax + zmargin)
        zmax += zmargin
        intv = Interval(Value(zmin), Value(zmax))
        if self.locator is None:
            self.locator = MaxNLocator(N+1)
        self.locator.set_view_interval(intv)
        self.locator.set_data_interval(intv)
        lev = self.locator()
        if self.filled:
            return lev
        return lev[1:-1]
Example #8
0
    def _autolev(self, z, N):
        '''
        Select contour levels to span the data.

        We need two more levels for filled contours than for
        line contours, because for the latter we need to specify
        the lower and upper boundary of each range. For example,
        a single contour boundary, say at z = 0, requires only
        one contour line, but two filled regions, and therefore
        three levels to provide boundaries for both regions.
        '''
        zmax = ma.maximum(z)
        zmin = ma.minimum(z)
        zmargin = (zmax - zmin) * 0.001  # so z < (zmax + zmargin)
        zmax += zmargin
        intv = Interval(Value(zmin), Value(zmax))
        if self.locator is None:
            self.locator = MaxNLocator(N + 1)
        self.locator.set_view_interval(intv)
        self.locator.set_data_interval(intv)
        lev = self.locator()
        if self.filled:
            return lev
        return lev[1:-1]
Example #9
0
 def autoscale(self, A):
     if not self.scaled():
         if self.vmin is None: self.vmin = ma.minimum(A)
         if self.vmax is None: self.vmax = ma.maximum(A)
Example #10
0
    def __init__(self, ax, *args, **kwargs):
        """
        Draw contour lines or filled regions, depending on
        whether keyword arg 'filled' is False (default) or True.

        The first argument of the initializer must be an axes
        object.  The remaining arguments and keyword arguments
        are described in ContourSet.contour_doc.

        """
        self.ax = ax
        self.filled = kwargs.get('filled', False)
        self.linewidths = kwargs.get('linewidths', None)

        self.alpha = kwargs.get('alpha', 1.0)
        self.origin = kwargs.get('origin', None)
        self.extent = kwargs.get('extent', None)
        cmap = kwargs.get('cmap', None)
        self.colors = kwargs.get('colors', None)
        norm = kwargs.get('norm', None)
        self.clip_ends = kwargs.get('clip_ends', True)
        self.antialiased = kwargs.get('antialiased', True)
        self.nchunk = kwargs.get('nchunk', 0)

        if self.origin is not None: assert(self.origin in
                                            ['lower', 'upper', 'image'])
        if self.extent is not None: assert(len(self.extent) == 4)
        if cmap is not None: assert(isinstance(cmap, Colormap))
        if self.colors is not None and cmap is not None:
            raise ValueError('Either colors or cmap must be None')
        if self.origin == 'image': self.origin = rcParams['image.origin']
        x, y, z = self._contour_args(*args)        # also sets self.levels,
                                                   #  self.layers
        if self.colors is not None:
            cmap = ListedColormap(self.colors, N=len(self.layers))
        if self.filled:
            self.collections = silent_list('PolyCollection')
        else:
            self.collections = silent_list('LineCollection')
        # label lists must be initialized here
        self.cl = []
        self.cl_cvalues = []

        kw = {'cmap': cmap}
        if norm is not None:
            kw['norm'] = norm
        ScalarMappable.__init__(self, **kw) # sets self.cmap;
        self._process_colors()

        if self.filled:
            if self.linewidths is None:
                self.linewidths = 0.05 # Good default for Postscript.
            if iterable(self.linewidths):
                self.linewidths = self.linewidths[0]
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmaskorNone(z))
            lowers = self.levels[:-1]
            uppers = self.levels[1:]
            for level, level_upper, color in zip(lowers, uppers, self.tcolors):
                nlist = C.trace(level, level_upper, points = 1,
                        nchunk = self.nchunk)
                col = PolyCollection(nlist,
                                     linewidths = (self.linewidths,),
                                     antialiaseds = (self.antialiased,))
                col.set_color(color) # sets both facecolor and edgecolor
                self.ax.add_collection(col)
                self.collections.append(col)

        else:
            tlinewidths = self._process_linewidths()
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmaskorNone(z))
            for level, color, width in zip(self.levels, self.tcolors, tlinewidths):
                nlist = C.trace(level, points = 1)
                col = LineCollection(nlist)
                col.set_color(color)
                col.set_linewidth(width)

                if level < 0.0 and self.monochrome:
                    col.set_linestyle((0, (6.,6.)),)
                col.set_label(str(level))         # only for self-documentation
                self.ax.add_collection(col)
                self.collections.append(col)

        ## check: seems like set_xlim should also be inside
        if not self.ax.ishold():
            self.ax.cla()
        self.ax.set_xlim((ma.minimum(x), ma.maximum(x)))
        self.ax.set_ylim((ma.minimum(y), ma.maximum(y)))
Example #11
0
 def autoscale(self, A):
     if not self.scaled():
         if self.vmin is None: self.vmin = ma.minimum(A)
         if self.vmax is None: self.vmax = ma.maximum(A)
Example #12
0
    def _contour_args(self, *args):
        if self.filled: fn = 'contourf'
        else: fn = 'contour'
        Nargs = len(args)
        if Nargs <= 2:
            z = args[0]
            x, y = self._initialize_x_y(z)
        elif Nargs <= 4:
            x, y, z = self._check_xyz(args[:3])
        else:
            raise TypeError("Too many arguments to %s; see help(%s)" %
                            (fn, fn))
        z = ma.asarray(
            z)  # Convert to native masked array format if necessary.
        self.zmax = ma.maximum(z)
        self.zmin = ma.minimum(z)
        self._auto = False
        if self.levels is None:
            if Nargs == 1 or Nargs == 3:
                lev = self._autolev(z, 7)
            else:  # 2 or 4 args
                level_arg = args[-1]
                if type(level_arg) == int:
                    lev = self._autolev(z, level_arg)
                elif iterable(level_arg) and len(shape(level_arg)) == 1:
                    lev = array([float(fl) for fl in level_arg])
                else:
                    raise TypeError(
                        "Last %s arg must give levels; see help(%s)" %
                        (fn, fn))
            if self.filled and len(lev) < 2:
                raise ValueError("Filled contours require at least 2 levels.")
            # Workaround for cntr.c bug wrt masked interior regions:
            #if filled:
            #    z = ma.masked_array(z.filled(-1e38))
            # It's not clear this is any better than the original bug.
            self.levels = lev
        #if self._auto and self.extend in ('both', 'min', 'max'):
        #    raise TypeError("Auto level selection is inconsistent "
        #                             + "with use of 'extend' kwarg")
        self._levels = list(self.levels)
        if self.extend in ('both', 'min'):
            self._levels.insert(0, self.zmin - 1)
        if self.extend in ('both', 'max'):
            self._levels.append(self.zmax + 1)
        self._levels = asarray(self._levels)
        self.vmin = amin(self.levels)  # alternative would be self.layers
        self.vmax = amax(self.levels)
        if self.extend in ('both', 'min') or self.clip_ends:
            self.vmin = 2 * self.levels[0] - self.levels[1]
        if self.extend in ('both', 'max') or self.clip_ends:
            self.vmax = 2 * self.levels[-1] - self.levels[-2]
        self.layers = self._levels  # contour: a line is a thin layer
        if self.filled:
            self.layers = 0.5 * (self._levels[:-1] + self._levels[1:])
            if self.extend in ('both', 'min') or self.clip_ends:
                self.layers[0] = 0.5 * (self.vmin + self._levels[1])
            if self.extend in ('both', 'max') or self.clip_ends:
                self.layers[-1] = 0.5 * (self.vmax + self._levels[-2])

        return (x, y, z)
Example #13
0
    def __init__(self, ax, *args, **kwargs):
        """
        Draw contour lines or filled regions, depending on
        whether keyword arg 'filled' is False (default) or True.

        The first argument of the initializer must be an axes
        object.  The remaining arguments and keyword arguments
        are described in ContourSet.contour_doc.

        """
        self.ax = ax
        self.levels = kwargs.get('levels', None)
        self.filled = kwargs.get('filled', False)
        self.linewidths = kwargs.get('linewidths', None)

        self.alpha = kwargs.get('alpha', 1.0)
        self.origin = kwargs.get('origin', None)
        self.extent = kwargs.get('extent', None)
        cmap = kwargs.get('cmap', None)
        self.colors = kwargs.get('colors', None)
        norm = kwargs.get('norm', None)
        self.clip_ends = kwargs.get('clip_ends', None)  ########
        self.extend = kwargs.get('extend', 'neither')
        if self.clip_ends is not None:
            warnings.warn("'clip_ends' has been replaced by 'extend'")
            self.levels = self.levels[1:-1]  # discard specified end levels
            self.extend = 'both'  # regenerate end levels
        self.antialiased = kwargs.get('antialiased', True)
        self.nchunk = kwargs.get('nchunk', 0)
        self.locator = kwargs.get('locator', None)

        if self.origin is not None:
            assert (self.origin in ['lower', 'upper', 'image'])
        if self.extent is not None: assert (len(self.extent) == 4)
        if cmap is not None: assert (isinstance(cmap, Colormap))
        if self.colors is not None and cmap is not None:
            raise ValueError('Either colors or cmap must be None')
        if self.origin == 'image': self.origin = rcParams['image.origin']
        x, y, z = self._contour_args(*args)  # also sets self.levels,
        #  self.layers
        if self.colors is not None:
            cmap = ListedColormap(self.colors, N=len(self.layers))
        if self.filled:
            self.collections = silent_list('PolyCollection')
        else:
            self.collections = silent_list('LineCollection')
        # label lists must be initialized here
        self.cl = []
        self.cl_cvalues = []

        kw = {'cmap': cmap}
        if norm is not None:
            kw['norm'] = norm
        ScalarMappable.__init__(self, **kw)  # sets self.cmap;
        self._process_colors()

        if self.filled:
            if self.linewidths is None:
                self.linewidths = 0.05  # Good default for Postscript.
            if iterable(self.linewidths):
                self.linewidths = self.linewidths[0]
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmaskorNone(z))
            lowers = self._levels[:-1]
            uppers = self._levels[1:]
            for level, level_upper, color in zip(lowers, uppers, self.tcolors):
                nlist = C.trace(level,
                                level_upper,
                                points=0,
                                nchunk=self.nchunk)
                col = PolyCollection(nlist,
                                     linewidths=(self.linewidths, ),
                                     antialiaseds=(self.antialiased, ),
                                     facecolors=color,
                                     edgecolors='None')
                self.ax.add_collection(col)
                self.collections.append(col)

        else:
            tlinewidths = self._process_linewidths()
            self.tlinewidths = tlinewidths
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmaskorNone(z))
            for level, color, width in zip(self.levels, self.tcolors,
                                           tlinewidths):
                nlist = C.trace(level, points=0)
                col = LineCollection(nlist, colors=color, linewidths=width)

                if level < 0.0 and self.monochrome:
                    col.set_linestyle(
                        (0, rcParams['contour.negative_linestyle']))
                col.set_label(str(level))  # only for self-documentation
                self.ax.add_collection(col)
                self.collections.append(col)
        x0 = ma.minimum(x)
        x1 = ma.maximum(x)
        y0 = ma.minimum(y)
        y1 = ma.maximum(y)
        self.ax.update_datalim([(x0, y0), (x1, y1)])
        self.ax.set_xlim((x0, x1))
        self.ax.set_ylim((y0, y1))
Example #14
0
    def __init__(self, ax, *args, **kwargs):
        """
        Draw contour lines or filled regions, depending on
        whether keyword arg 'filled' is False (default) or True.

        The first argument of the initializer must be an axes
        object.  The remaining arguments and keyword arguments
        are described in ContourSet.contour_doc.

        """
        self.ax = ax
        self.filled = kwargs.get('filled', False)
        self.linewidths = kwargs.get('linewidths', None)

        self.alpha = kwargs.get('alpha', 1.0)
        self.origin = kwargs.get('origin', None)
        self.extent = kwargs.get('extent', None)
        cmap = kwargs.get('cmap', None)
        self.colors = kwargs.get('colors', None)
        self.clip_ends = kwargs.get('clip_ends', True)
        self.antialiased = kwargs.get('antialiased', True)
        self.nchunk = kwargs.get('nchunk', 0)

        if self.origin is not None: assert(self.origin in
                                            ['lower', 'upper', 'image'])
        if self.extent is not None: assert(len(self.extent) == 4)
        if cmap is not None: assert(isinstance(cmap, Colormap))
        if self.colors is not None and cmap is not None:
            raise ValueError('Either colors or cmap must be None')
        if self.origin == 'image': self.origin = rcParams['image.origin']
        x, y, z = self._contour_args(*args)        # also sets self.levels,
                                                   #  self.layers
        if self.colors is not None:
            cmap = ListedColormap(self.colors, N=len(self.layers))
        if self.filled:
            self.collections = silent_list('PolyCollection')
        else:
            self.collections = silent_list('LineCollection')
        # label lists must be initialized here
        self.cl = []
        self.cl_cvalues = []

        ScalarMappable.__init__(self, cmap = cmap) # sets self.cmap;
                                                   # default norm for now
        self._process_colors()


        if self.filled:
            if self.linewidths is None:
                self.linewidths = 0.05 # Good default for Postscript.
            if iterable(self.linewidths):
                self.linewidths = self.linewidths[0]
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmask(z))
            lowers = self.levels[:-1]
            uppers = self.levels[1:]
            for level, level_upper, color in zip(lowers, uppers, self.tcolors):
                nlist = C.trace(level, level_upper, points = 1,
                        nchunk = self.nchunk)
                col = PolyCollection(nlist,
                                     linewidths = (self.linewidths,),
                                     antialiaseds = (self.antialiased,))
                col.set_color(color) # sets both facecolor and edgecolor
                self.ax.add_collection(col)
                self.collections.append(col)

        else:
            tlinewidths = self._process_linewidths()
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmask(z))
            for level, color, width in zip(self.levels, self.tcolors, tlinewidths):
                nlist = C.trace(level, points = 1)
                col = LineCollection(nlist)
                col.set_color(color)
                col.set_linewidth(width)

                if level < 0.0 and self.monochrome:
                    col.set_linestyle((0, (6.,6.)),)
                    #print "setting dashed"
                col.set_label(str(level))         # only for self-documentation
                self.ax.add_collection(col)
                self.collections.append(col)

        ## check: seems like set_xlim should also be inside
        if not self.ax.ishold():
            self.ax.cla()
        self.ax.set_xlim((ma.minimum(x), ma.maximum(x)))
        self.ax.set_ylim((ma.minimum(y), ma.maximum(y)))
Example #15
0
    def __init__(self, ax, *args, **kwargs):
        """
        Draw contour lines or filled regions, depending on
        whether keyword arg 'filled' is False (default) or True.

        The first argument of the initializer must be an axes
        object.  The remaining arguments and keyword arguments
        are described in ContourSet.contour_doc.

        """
        self.ax = ax
        self.levels = kwargs.get('levels', None)
        self.filled = kwargs.get('filled', False)
        self.linewidths = kwargs.get('linewidths', None)

        self.alpha = kwargs.get('alpha', 1.0)
        self.origin = kwargs.get('origin', None)
        self.extent = kwargs.get('extent', None)
        cmap = kwargs.get('cmap', None)
        self.colors = kwargs.get('colors', None)
        norm = kwargs.get('norm', None)
        self.clip_ends = kwargs.get('clip_ends', None)      ########
        self.extend = kwargs.get('extend', 'neither')
        if self.clip_ends is not None:
            warnings.warn("'clip_ends' has been replaced by 'extend'")
            self.levels = self.levels[1:-1] # discard specified end levels
            self.extend = 'both'            # regenerate end levels
        self.antialiased = kwargs.get('antialiased', True)
        self.nchunk = kwargs.get('nchunk', 0)
        self.locator = kwargs.get('locator', None)

        if self.origin is not None: assert(self.origin in
                                            ['lower', 'upper', 'image'])
        if self.extent is not None: assert(len(self.extent) == 4)
        if cmap is not None: assert(isinstance(cmap, Colormap))
        if self.colors is not None and cmap is not None:
            raise ValueError('Either colors or cmap must be None')
        if self.origin == 'image': self.origin = rcParams['image.origin']
        x, y, z = self._contour_args(*args)        # also sets self.levels,
                                                   #  self.layers
        if self.colors is not None:
            cmap = ListedColormap(self.colors, N=len(self.layers))
        if self.filled:
            self.collections = silent_list('PolyCollection')
        else:
            self.collections = silent_list('LineCollection')
        # label lists must be initialized here
        self.cl = []
        self.cl_cvalues = []

        kw = {'cmap': cmap}
        if norm is not None:
            kw['norm'] = norm
        ScalarMappable.__init__(self, **kw) # sets self.cmap;
        self._process_colors()

        if self.filled:
            if self.linewidths is None:
                self.linewidths = 0.05 # Good default for Postscript.
            if iterable(self.linewidths):
                self.linewidths = self.linewidths[0]
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmaskorNone(z))
            lowers = self._levels[:-1]
            uppers = self._levels[1:]
            for level, level_upper, color in zip(lowers, uppers, self.tcolors):
                nlist = C.trace(level, level_upper, points = 0,
                        nchunk = self.nchunk)
                col = PolyCollection(nlist,
                                     linewidths = (self.linewidths,),
                                     antialiaseds = (self.antialiased,),
                                     facecolors= color,
                                     edgecolors= 'None')
                self.ax.add_collection(col)
                self.collections.append(col)

        else:
            tlinewidths = self._process_linewidths()
            self.tlinewidths = tlinewidths
            #C = _contour.Cntr(x, y, z.filled(), z.mask())
            C = _contour.Cntr(x, y, z.filled(), ma.getmaskorNone(z))
            for level, color, width in zip(self.levels, self.tcolors, tlinewidths):
                nlist = C.trace(level, points = 0)
                col = LineCollection(nlist,
                                     colors = color,
                                     linewidths = width)

                if level < 0.0 and self.monochrome:
                    col.set_linestyle((0, rcParams['contour.negative_linestyle']))
                col.set_label(str(level))         # only for self-documentation
                self.ax.add_collection(col)
                self.collections.append(col)
        x0 = ma.minimum(x)
        x1 = ma.maximum(x)
        y0 = ma.minimum(y)
        y1 = ma.maximum(y)
        self.ax.update_datalim([(x0,y0), (x1,y1)])
        self.ax.set_xlim((x0, x1))
        self.ax.set_ylim((y0, y1))