ticker.EngFormatter: Simplify by always using self.orderOfMagnitude = 0

doronbehar · doronbehar · commit 1074bb8b8ef3 · 2024-07-04T00:25:25.000+03:00
diff --git a/doc/users/next_whats_new/EngFormatter-offset.rst b/doc/users/next_whats_new/EngFormatter-offset.rst
@@ -18,9 +18,8 @@ Here's an example result:
     import matplotlib.ticker as mticker
 
     fig, ax = plt.subplots()
-    offset = int(1e7)
-    ydata = range(offset, offset+5)
+    data_offset = 10000000
+    ydata = range(data_offset, data_offset+5)
     ax.plot(ydata)
-    ax.set_yticks(ydata)
     ax.yaxis.set_major_formatter(mticker.EngFormatter(useOffset=True, unit="Hz"))
     plt.show()
diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -1596,14 +1596,17 @@ def test_engformatter_usetex_useMathText():
 
 def test_engformatter_useOffset():
     fig, ax = plt.subplots()
-    offset = int(1e7)
-    ydata = range(offset, offset+5)
+    data_offset = 10000000
+    ydata = range(data_offset, data_offset+5)
     ax.plot(ydata)
     ax.set_yticks(ydata)
     ax.yaxis.set_major_formatter(mticker.EngFormatter(useOffset=True, unit="Hz"))
     fig.canvas.draw()
     y_tick_label_text = [labl.get_text() for labl in ax.get_yticklabels()]
-    assert y_tick_label_text == (np.array(ydata)-offset).astype(str).tolist()
+    offset = ax.yaxis.get_major_formatter().get_offset()
+    expectedTicks = list(map("{} Hz".format, np.array(ydata) - data_offset))
+    assert y_tick_label_text == expectedTicks
+    assert "+10 MHz" == offset
 
 
 class TestPercentFormatter:
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -1432,13 +1432,16 @@ def __call__(self, x, pos=None):
         if len(self.locs) == 0 or self.offset == 0:
             return self.fix_minus(self.format_data(x))
         else:
-            xp = (x - self.offset) / (10. ** self.orderOfMagnitude)
+            # Here in ScalarFormatter.__call__ we also check
+            # self.orderOfMagnitude. In this class, it is always 0, since the
+            # oom of the data is represented by the ENG_PREFIXES prepending
+            # the ticks.
+            xp = x - self.offset
             if abs(xp) < 1e-8:
                 xp = 0
-            # The ScalarFormatter.__call__ reads the locale here as well. We
-            # don't care about it, and we want the ticks to also get the unit
-            # with the best prefix as computed by self.format_data that is
-            # produced by it doesn't.
+            # Also in contrary to ScalarFormatter.__call__ we use the
+            # conditioned tex formatting provided by self.format_data and we
+            # don't care about the locale.
             return self.fix_minus(self.format_data(xp))
 
     def set_locs(self, locs):
@@ -1447,41 +1450,21 @@ def set_locs(self, locs):
         if len(self.locs) > 0:
             if self._useOffset:
                 self._compute_offset()
-            self._set_order_of_magnitude()
-            # This is what's different from ScalarFormatter: We search among
-            # the engineers' standard orders of magnitudes (0, -3, 3, -6, 6,
-            # -9, 9 etc) the oom closest to our self.orderOfMagnitude. Then we
-            # set our self.orderOfMagnitude to it.
-            c = abs(self.orderOfMagnitude)
-            for sciOom in itertools.count(0, 3):
-                if c <= sciOom:
-                    self.orderOfMagnitude = math.copysign(sciOom, self.orderOfMagnitude)
-                    break
-            self._set_format()
 
     # Simplify a bit ScalarFormatter.get_offset: We always want to use
-    # self.format_data. We insert here the surrounding $...$ here, if tex /
-    # mathtext is set.
+    # self.format_data, and we don't need to handle tex related features as
+    # these are handled well by self.format_data. Also we don't need to check
+    # self.orderOfMagnitude since we want it to always be 0, because the ticks
+    # themselves represetnt the order of magnitude of the data much better.
     def get_offset(self):
         # docstring inherited
         if len(self.locs) == 0:
             return ''
-        if self.orderOfMagnitude or self.offset:
-            offsetStr = ''
-            sciNotStr = ''
-            if self.offset:
-                offsetStr = self.format_data(self.offset)
-                if self.offset > 0:
-                    offsetStr = '+' + offsetStr
-            if self.orderOfMagnitude:
-                sciNotStr = self.format_data(10 ** self.orderOfMagnitude)
-            if self._useMathText or self._usetex:
-                if sciNotStr != '':
-                    sciNotStr = r'\times%s' % sciNotStr
-                s = fr'${sciNotStr}{offsetStr}$'
-            else:
-                s = ''.join((sciNotStr, offsetStr))
-            return self.fix_minus(s)
+        if self.offset:
+            offsetStr = self.format_data(self.offset)
+            if self.offset > 0:
+                offsetStr = '+' + offsetStr
+            return self.fix_minus(offsetStr)
         return ''
 
     def format_eng(self, num):
