Improve the minor tick labeling by LogFormatter.

efiring · NelleV · commit f718a3b73879 · 2016-11-24T10:24:21.000-08:00
diff --git a/lib/matplotlib/scale.py b/lib/matplotlib/scale.py
@@ -251,8 +251,7 @@ def set_default_locators_and_formatters(self, axis):
         axis.set_minor_locator(LogLocator(self.base, self.subs))
         axis.set_minor_formatter(
             LogFormatterSciNotation(self.base,
-                                    labelOnlyBase=self.subs,
-                                    label_pruning=True))
+                                    labelOnlyBase=self.subs))
 
     def get_transform(self):
         """
diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -241,9 +241,7 @@ def test_LogFormatter_sublabel():
     ax.xaxis.set_minor_locator(mticker.LogLocator(base=10,
                                                   subs=np.arange(2, 10)))
     ax.xaxis.set_major_formatter(mticker.LogFormatter(labelOnlyBase=True))
-    ax.xaxis.set_minor_formatter(mticker.LogFormatter(
-        labelOnlyBase=False,
-        label_pruning=True))
+    ax.xaxis.set_minor_formatter(mticker.LogFormatter(labelOnlyBase=False))
     # axis range above 3 decades, only bases are labeled
     ax.set_xlim(1, 1e4)
     fmt = ax.xaxis.get_major_formatter()
@@ -263,9 +261,13 @@ def test_LogFormatter_sublabel():
     ax.set_xlim(1, 80)
     _sub_labels(ax.xaxis, subs=[])
 
-    # axis range at 0 to 1 decades, label subs 2, 3, 6
+    # axis range at 0.4 to 1 decades, label subs 2, 3, 4, 6
     ax.set_xlim(1, 8)
-    _sub_labels(ax.xaxis, subs=[2, 3, 6])
+    _sub_labels(ax.xaxis, subs=[2, 3, 4, 6])
+
+    # axis range at 0 to 0.4 decades, label all
+    ax.set_xlim(0.5, 0.9)
+    _sub_labels(ax.xaxis, subs=np.arange(2, 10, dtype=int))
 
 
 def _logfe_helper(formatter, base, locs, i, expected_result):
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -801,7 +801,7 @@ class LogFormatter(Formatter):
     Format values for log axis.
     """
     def __init__(self, base=10.0, labelOnlyBase=False,
-                 label_pruning=False):
+                 minor_thresholds=(1, 0.4)):
         """
         `base` is used to locate the decade tick, which will be the only
         one to be labeled if `labelOnlyBase` is ``True``.
@@ -812,15 +812,21 @@ def __init__(self, base=10.0, labelOnlyBase=False,
             base of the logarithm.
 
         labelOnlyBase : bool, optional, default: False
-            whether to only label decades ticks.
+            whether label ticks only at integer multiples of base.
+            This is normally True for major ticks and False for
+            minor ticks.
 
-        label_pruning : bool, optional, default: False
-            when set to True, label on a subset of ticks.
+        minor_thresholds : (subset, all), optional, default: (1, 0.4)
+            Thresholds applied to the data range measured in powers
+            of the base (numbers of "decades", or 'numdec'), and
+            effective only when labelOnlyBase is False.  Then a
+            subset of minor ticks will be labeled if `numdec <= subset`,
+            and all will be labeled if `numdec <= all`.
         """
         self._base = base + 0.0
         self.labelOnlyBase = labelOnlyBase
-        self.label_pruning = label_pruning
-        self._sublabels = [1, ]
+        self.minor_thresholds = minor_thresholds
+        self._sublabels = None
 
     def base(self, base):
         """
@@ -872,13 +878,15 @@ def set_locs(self, locs):
             vmax = math.log(vmax) / math.log(b)
             numdec = abs(vmax - vmin)
 
-        if numdec > 1:
+        if numdec > self.minor_thresholds[0]:
             # Label only bases
             self._sublabels = set((1,))
-        else:
+        elif numdec > self.minor_thresholds[1]:
             # Add labels between bases at log-spaced coefficients
-            c = np.logspace(0, 1, (4 - int(numdec)) + 1, base=b)
+            c = np.logspace(0, 1, b//2 + 1, base=b)[1:-1]
             self._sublabels = set(np.round(c))
+        else:
+            self._sublabels = set(np.linspace(2, b-1, b-2))
 
     def __call__(self, x, pos=None):
         """
@@ -895,9 +903,9 @@ def __call__(self, x, pos=None):
         exponent = np.round(fx) if isDecade else np.floor(fx)
         coeff = np.round(x / b ** exponent)
 
-        if self.label_pruning and coeff not in self._sublabels:
+        if self.labelOnlyBase and not isDecade:
             return ''
-        if not isDecade and self.labelOnlyBase:
+        if self._sublabels is not None and coeff not in self._sublabels:
             return ''
 
         if x > 10000:
@@ -972,16 +980,17 @@ def __call__(self, x, pos=None):
         if x == 0:
             return '0'
         sign = np.sign(x)
+        x = abs(x)
         # only label the decades
-        fx = math.log(abs(x)) / math.log(b)
+        fx = math.log(x) / math.log(b)
 
         isDecade = is_close_to_int(fx)
         exponent = np.round(fx) if isDecade else np.floor(fx)
-        coeff = np.round(abs(x) / b ** exponent)
+        coeff = np.round(x / b ** exponent)
 
-        if self.label_pruning and coeff not in self._sublabels:
+        if self.labelOnlyBase and not isDecade:
             return ''
-        if not isDecade and self.labelOnlyBase:
+        if self._sublabels is not None and coeff not in self._sublabels:
             return ''
 
         if abs(fx) > 10000:
@@ -1039,9 +1048,9 @@ def __call__(self, x, pos=None):
         else:
             base = '%s' % b
 
-        if self.label_pruning and coeff not in self._sublabels:
+        if self.labelOnlyBase and not isDecade:
             return ''
-        if not is_decade and self.labelOnlyBase:
+        if self._sublabels is not None and coeff not in self._sublabels:
             return ''
 
         if not is_decade:
