Merge pull request #1057 from efiring/contour_norm_scaling

Contour norm scaling

CHANGELOG

@@ -1,9 +1,17 @@
+2012-08-05 When a norm is passed to contourf, either or both of the
+           vmin, vmax attributes of that norm are now respected.
+           Formerly they were respected only if both were
+           specified. In addition, vmin and/or vmax can now
+           be passed to contourf directly as kwargs. - EF
+
 2012-07-24 Contourf handles the extend kwarg by mapping the extended
            ranges outside the normed 0-1 range so that they are
            handled by colormap colors determined by the set_under
            and set_over methods.  Previously the extended ranges
            were mapped to 0 or 1 so that the "under" and "over"
-           colormap colors were ignored. - EF
+           colormap colors were ignored. This change also increases
+           slightly the color contrast for a given set of contour
+           levels. - EF
 
 2012-06-24 Make use of mathtext in tick labels configurable - DSD
 

lib/matplotlib/axes.py

@@ -3754,7 +3754,7 @@ def vlines(self, x, ymin, ymax, colors='k', linestyles='solid',
                                     linestyles=linestyles, label=label)
         self.add_collection(coll)
         coll.update(kwargs)
-      
+
         if len(x) > 0:
             minx = min( x )
             maxx = max( x )
@@ -6955,16 +6955,18 @@ def pcolor(self, *args, **kwargs):
             A :class:`matplotlib.colors.Colormap` instance. If *None*, use
             rc settings.
 
-          norm: [ *None* | Normalize ]
+          *norm*: [ *None* | Normalize ]
             An :class:`matplotlib.colors.Normalize` instance is used
             to scale luminance data to 0,1. If *None*, defaults to
             :func:`normalize`.
 
           *vmin*/*vmax*: [ *None* | scalar ]
             *vmin* and *vmax* are used in conjunction with *norm* to
-            normalize luminance data.  If either are *None*, the min
-            and max of the color array *C* is used.  If you pass a
-            *norm* instance, *vmin* and *vmax* will be ignored.
+            normalize luminance data.  If either is *None*, it
+            is autoscaled to the respective min or max
+            of the color array *C*.  If not *None*, *vmin* or
+            *vmax* passed in here override any pre-existing values
+            supplied in the *norm* instance.
 
           *shading*: [ 'flat' | 'faceted' ]
             If 'faceted', a black grid is drawn around each rectangle; if
@@ -7121,10 +7123,8 @@ def pcolor(self, *args, **kwargs):
         if norm is not None: assert(isinstance(norm, mcolors.Normalize))
         collection.set_cmap(cmap)
         collection.set_norm(norm)
-        if vmin is not None or vmax is not None:
-            collection.set_clim(vmin, vmax)
-        else:
-            collection.autoscale_None()
+        collection.set_clim(vmin, vmax)
+        collection.autoscale_None()
         self.grid(False)
 
         x = X.compressed()
@@ -7167,9 +7167,11 @@ def pcolormesh(self, *args, **kwargs):
 
           *vmin*/*vmax*: [ *None* | scalar ]
             *vmin* and *vmax* are used in conjunction with *norm* to
-            normalize luminance data.  If either are *None*, the min
-            and max of the color array *C* is used.  If you pass a
-            *norm* instance, *vmin* and *vmax* will be ignored.
+            normalize luminance data.  If either is *None*, it
+            is autoscaled to the respective min or max
+            of the color array *C*.  If not *None*, *vmin* or
+            *vmax* passed in here override any pre-existing values
+            supplied in the *norm* instance.
 
           *shading*: [ 'flat' | 'gouraud' ]
             'flat' indicates a solid color for each quad.  When
@@ -7235,10 +7237,8 @@ def pcolormesh(self, *args, **kwargs):
         if norm is not None: assert(isinstance(norm, mcolors.Normalize))
         collection.set_cmap(cmap)
         collection.set_norm(norm)
-        if vmin is not None or vmax is not None:
-            collection.set_clim(vmin, vmax)
-        else:
-            collection.autoscale_None()
+        collection.set_clim(vmin, vmax)
+        collection.autoscale_None()
 
         self.grid(False)
 

lib/matplotlib/colorbar.py

@@ -255,7 +255,7 @@ def __init__(self, ax, cmap=None,
         self.filled = filled
         self.extendfrac = extendfrac
         self.solids = None
-        self.lines = None
+        self.lines = list()
         self.outline = None
         self.patch = None
         self.dividers = None
@@ -467,14 +467,25 @@ def _add_solids(self, X, Y, C):
                               )
             self.ax.add_collection(self.dividers)
 
-    def add_lines(self, levels, colors, linewidths):
+    def add_lines(self, levels, colors, linewidths, erase=True):
         '''
         Draw lines on the colorbar.
+
+        *colors* and *linewidths* must be scalars or
+        sequences the same length as *levels*.
+
+        Set *erase* to False to add lines without first
+        removing any previously added lines.
         '''
-        N = len(levels)
-        dummy, y = self._locate(levels)
-        if len(y) != N:
-            raise ValueError("levels are outside colorbar range")
+        y = self._locate(levels)
+        nlevs = len(levels)
+        igood = (y < 1.001) & (y > -0.001)
+        y = y[igood]
+        if cbook.iterable(colors):
+            colors = np.asarray(colors)[igood]
+        if cbook.iterable(linewidths):
+            linewidths = np.asarray(linewidths)[igood]
+        N = len(y)
         x = np.array([0.0, 1.0])
         X, Y = np.meshgrid(x,y)
         if self.orientation == 'vertical':
@@ -483,9 +494,10 @@ def add_lines(self, levels, colors, linewidths):
             xy = [zip(Y[i], X[i]) for i in xrange(N)]
         col = collections.LineCollection(xy, linewidths=linewidths)
 
-        if self.lines:
-            self.lines.remove()
-        self.lines = col
+        if erase and self.lines:
+            for lc in self.lines.pop():
+                lc.remove()
+        self.lines.append(col)
         col.set_color(colors)
         self.ax.add_collection(col)
 
@@ -528,7 +540,10 @@ def _ticker(self):
         locator.axis.get_minpos = lambda : intv[0]
         formatter.axis.get_minpos = lambda : intv[0]
         b = np.array(locator())
-        b, ticks = self._locate(b)
+        ticks = self._locate(b)
+        inrange = (ticks > -0.001) & (ticks < 1.001)
+        ticks = ticks[inrange]
+        b = b[inrange]
         formatter.set_locs(b)
         ticklabels = [formatter(t, i) for i, t in enumerate(b)]
         offset_string = formatter.get_offset()
@@ -746,37 +761,36 @@ def _mesh(self):
 
     def _locate(self, x):
         '''
-        Given a possible set of color data values, return the ones
-        within range, together with their corresponding colorbar
-        data coordinates.
+        Given a set of color data values, return their
+        corresponding colorbar data coordinates.
         '''
         if isinstance(self.norm, (colors.NoNorm, colors.BoundaryNorm)):
             b = self._boundaries
             xn = x
-            xout = x
         else:
             # Do calculations using normalized coordinates so
             # as to make the interpolation more accurate.
             b = self.norm(self._boundaries, clip=False).filled()
-            # We do our own clipping so that we can allow a tiny
-            # bit of slop in the end point ticks to allow for
-            # floating point errors.
             xn = self.norm(x, clip=False).filled()
-            in_cond = (xn > -0.001) & (xn < 1.001)
-            xn = np.compress(in_cond, xn)
-            xout = np.compress(in_cond, x)
-        # The rest is linear interpolation with clipping.
+        # The rest is linear interpolation with extrapolation at ends.
         y = self._y
         N = len(b)
-        ii = np.minimum(np.searchsorted(b, xn), N-1)
-        i0 = np.maximum(ii - 1, 0)
+        ii = np.searchsorted(b, xn)
+        i0 = ii - 1
+        itop = (ii == N)
+        ibot = (ii == 0)
+        i0[itop] -= 1
+        ii[itop] -= 1
+        i0[ibot] += 1
+        ii[ibot] += 1
+
         #db = b[ii] - b[i0]
         db = np.take(b, ii) - np.take(b, i0)
-        db = np.where(i0==ii, 1.0, db)
         #dy = y[ii] - y[i0]
         dy = np.take(y, ii) - np.take(y, i0)
         z = np.take(y, i0) + (xn-np.take(b,i0))*dy/db
-        return xout, z
+
+        return z
 
     def set_alpha(self, alpha):
         self.alpha = alpha
@@ -834,10 +848,13 @@ def on_mappable_changed(self, mappable):
         self.set_clim(mappable.get_clim())
         self.update_normal(mappable)
 
-    def add_lines(self, CS):
+    def add_lines(self, CS, erase=True):
         '''
         Add the lines from a non-filled
         :class:`~matplotlib.contour.ContourSet` to the colorbar.
+
+        Set *erase* to False if these lines should be added to
+        any pre-existing lines.
         '''
         if not isinstance(CS, contour.ContourSet) or CS.filled:
             raise ValueError('add_lines is only for a ContourSet of lines')
@@ -851,7 +868,8 @@ def add_lines(self, CS):
         #tcolors = [col.get_colors()[0] for col in CS.collections]
         #tlinewidths = [col.get_linewidth()[0] for lw in CS.collections]
         #print 'tlinewidths:', tlinewidths
-        ColorbarBase.add_lines(self, CS.levels, tcolors, tlinewidths)
+        ColorbarBase.add_lines(self, CS.levels, tcolors, tlinewidths,
+                                erase=erase)
 
     def update_normal(self, mappable):
         '''
@@ -884,7 +902,7 @@ def update_bruteforce(self, mappable):
         self.outline = None
         self.patch = None
         self.solids = None
-        self.lines = None
+        self.lines = list()
         self.dividers = None
         self.set_alpha(mappable.get_alpha())
         self.cmap = mappable.cmap

lib/matplotlib/colors.py

@@ -510,11 +510,10 @@ def __call__(self, X, alpha=None, bytes=False):
             xa = np.array([X])
         else:
             vtype = 'array'
-            xma = ma.array(X, copy=False)
-            mask_bad = xma.mask
-            xa = xma.data.copy()   # Copy here to avoid side effects.
+            xma = ma.array(X, copy=True)  # Copy here to avoid side effects.
+            mask_bad = xma.mask           # Mask will be used below.
+            xa = xma.filled()             # Fill to avoid infs, etc.
             del xma
-            # masked values are substituted below; no need to fill them here
 
         if xa.dtype.char in np.typecodes['Float']:
             # Treat 1.0 as slightly less than 1.