Merge pull request matplotlib#1686 from dhyams/fix_lost_ticks

efiring · efiring · commit 1aa61e301eb7 · 2013-02-18T19:14:18.000-08:00
Fix lost ticks
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -16,6 +16,7 @@
 import matplotlib.transforms as mtransforms
 import matplotlib.units as munits
 import numpy as np
+import warnings
 
 GRIDLINE_INTERPOLATION_STEPS = 180
 
@@ -972,11 +973,36 @@ def _update_ticks(self, renderer):
                 tick_tups = [ti for ti in tick_tups
                              if (ti[1] >= ilow) and (ti[1] <= ihigh)]
 
+        # so that we don't lose ticks on the end, expand out the interval ever so slightly.  The
+        # "ever so slightly" is defined to be the width of a half of a pixel.  We don't want to draw
+        # a tick that even one pixel outside of the defined axis interval.
+        if interval[0] <= interval[1]:
+            interval_expanded = interval
+        else:
+            interval_expanded = interval[1], interval[0]
+        
+        if hasattr(self, '_get_pixel_distance_along_axis'):
+            # normally, one does not want to catch all exceptions that could possibly happen, but it
+            # is not clear exactly what exceptions might arise from a user's projection (their rendition
+            # of the Axis object).  So, we catch all, with the idea that one would rather potentially
+            # lose a tick from one side of the axis or another, rather than see a stack trace.
+            try:
+               ds1 = self._get_pixel_distance_along_axis(interval_expanded[0], -0.5) 
+            except:
+               warnings.warn("Unable to find pixel distance along axis for interval padding; assuming no interval padding needed.")
+               ds1 = 0.0
+            try:
+               ds2 = self._get_pixel_distance_along_axis(interval_expanded[1], +0.5) 
+            except:
+               warnings.warn("Unable to find pixel distance along axis for interval padding; assuming no interval padding needed.")
+               ds2 = 0.0
+            interval_expanded = (interval[0] - ds1, interval[1] + ds2)
+
         ticks_to_draw = []
         for tick, loc, label in tick_tups:
             if tick is None:
                 continue
-            if not mtransforms.interval_contains(interval, loc):
+            if not mtransforms.interval_contains(interval_expanded, loc):
                 continue
             tick.update_position(loc)
             tick.set_label1(label)
@@ -1599,6 +1625,35 @@ def _get_offset_text(self):
         self.offset_text_position = 'bottom'
         return offsetText
 
+    def _get_pixel_distance_along_axis(self, where, perturb):
+        """
+        Returns the amount, in data coordinates, that a single pixel corresponds to in the
+        locality given by "where", which is also given in data coordinates, and is an x coordinate.
+        "perturb" is the amount to perturb the pixel.  Usually +0.5 or -0.5.
+
+        Implementing this routine for an axis is optional; if present, it will ensure that no
+        ticks are lost due to round-off at the extreme ends of an axis.
+        """
+        
+        # Note that this routine does not work for a polar axis, because of the 1e-10 below.  To
+        # do things correctly, we need to use rmax instead of 1e-10 for a polar axis.  But
+        # since we do not have that kind of information at this point, we just don't try to 
+        # pad anything for the theta axis of a polar plot.  
+        if self.axes.name == 'polar':
+           return 0.0
+
+        #
+        # first figure out the pixel location of the "where" point.  We use 1e-10 for the
+        # y point, so that we remain compatible with log axes.
+        #
+        trans = self.axes.transData     # transformation from data coords to display coords
+        transinv = trans.inverted()     # transformation from display coords to data coords
+        pix  = trans.transform_point((where, 1e-10))
+        ptp  = transinv.transform_point((pix[0] + perturb, pix[1])) # perturb the pixel.
+        dx   = abs(ptp[0] - where)
+        
+        return dx
+
     def get_label_position(self):
         """
         Return the label position (top or bottom)
@@ -1874,6 +1929,27 @@ def _get_offset_text(self):
         self.offset_text_position = 'left'
         return offsetText
 
+    def _get_pixel_distance_along_axis(self, where, perturb):
+        """
+        Returns the amount, in data coordinates, that a single pixel corresponds to in the
+        locality given by "where", which is also given in data coordinates, and is an y coordinate.
+        "perturb" is the amount to perturb the pixel.  Usually +0.5 or -0.5.
+
+        Implementing this routine for an axis is optional; if present, it will ensure that no
+        ticks are lost due to round-off at the extreme ends of an axis.
+        """
+
+        #        
+        # first figure out the pixel location of the "where" point.  We use 1e-10 for the
+        # x point, so that we remain compatible with log axes.
+        #
+        trans = self.axes.transData     # transformation from data coords to display coords
+        transinv = trans.inverted()     # transformation from display coords to data coords
+        pix  = trans.transform_point((1e-10, where))
+        ptp  = transinv.transform_point((pix[0], pix[1] + perturb)) # perturb the pixel.
+        dy   = abs(ptp[1] - where)
+        return dy
+
     def get_label_position(self):
         """
         Return the label position (left or right)
diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -26,7 +26,7 @@ def test_LinearLocator():
 
 def test_MultipleLocator():
     loc = mticker.MultipleLocator(base=3.147)
-    test_value = np.array([-6.294, -3.147, 0., 3.147, 6.294, 9.441])
+    test_value = np.array([-9.441, -6.294, -3.147, 0., 3.147, 6.294, 9.441, 12.588])
     assert_almost_equal(loc.tick_values(-7, 10), test_value)
 
 
@@ -35,12 +35,12 @@ def test_LogLocator():
 
     assert_raises(ValueError, loc.tick_values, 0, 1000)
 
-    test_value = np.array([1.00000000e-03, 1.00000000e-01, 1.00000000e+01,
-                           1.00000000e+03, 1.00000000e+05, 1.00000000e+07])
+    test_value = np.array([1.00000000e-05, 1.00000000e-03, 1.00000000e-01, 1.00000000e+01,
+                           1.00000000e+03, 1.00000000e+05, 1.00000000e+07, 1.000000000e+09])
     assert_almost_equal(loc.tick_values(0.001, 1.1e5), test_value)
 
     loc = mticker.LogLocator(base=2)
-    test_value = np.array([1., 2., 4., 8., 16., 32., 64., 128.])
+    test_value = np.array([0.5, 1., 2., 4., 8., 16., 32., 64., 128., 256.])
     assert_almost_equal(loc.tick_values(1, 100), test_value)
 
 
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -1165,7 +1165,7 @@ def tick_values(self, vmin, vmax):
         vmin = self._base.ge(vmin)
         base = self._base.get_base()
         n = (vmax - vmin + 0.001 * base) // base
-        locs = vmin + np.arange(n + 1) * base
+        locs = vmin - base + np.arange(n + 3) * base
         return self.raise_if_exceeds(locs)
 
     def view_limits(self, dmin, dmax):
@@ -1450,8 +1450,8 @@ def tick_values(self, vmin, vmax):
         while numdec / stride + 1 > self.numticks:
             stride += 1
 
-        decades = np.arange(math.floor(vmin),
-                            math.ceil(vmax) + stride, stride)
+        decades = np.arange(math.floor(vmin) - stride,
+                            math.ceil(vmax) + 2 * stride, stride)
         if hasattr(self, '_transform'):
             ticklocs = self._transform.inverted().transform(decades)
             if len(subs) > 1 or (len(subs == 1) and subs[0] != 1.0):
