Use exponent notation for log_format bases

has2k1 · Sep 28, 2022 · 3458383 · 3458383
1 parent 78b6236
commit 3458383
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diff --git a/doc/changelog.rst b/doc/changelog.rst
@@ -13,6 +13,11 @@ Bug Fixes
   where formatting for bases 2, 8 and 16 would fail if the values were
   float-integers.
 
+Enhancements
+************
+- :class:`~mizani.formatters.log_format` now uses exponent notation
+  for bases other than base 10.
+
 v0.8.0
 ------
 

diff --git a/mizani/formatters.py b/mizani/formatters.py
@@ -489,26 +489,30 @@ def __call__(self, x):
                 fmt = '{:1.0e}'
             else:
                 fmt = '{:g}'
-        elif self.base == 2:
-            fmt = '{:b}'
-        elif self.base == 8:
-            fmt = '{:o}'
-        elif self.base == 16:
-            fmt = '{:x}'
+            labels = [fmt.format(num) for num in x]
+            return self._tidyup_labels(labels)
         else:
-            warn("Formating values as base = 10")
-            fmt = '{:g}'
-
-        # Base 2, 8 & 16 formatters work with integers
-        if self.base != 10:
-            x = [
-                int(f)
-                if isinstance(f, float) and float.is_integer(f)
-                else f
-                for f in x
-            ]
-        labels = [fmt.format(num) for num in x]
-        return self._tidyup_labels(labels)
+            def _exp(num, base):
+                e = np.log(num)/np.log(base)
+                if float.is_integer(e):
+                    e = int(e)
+                else:
+                    e = np.round(e, 3)
+                return e
+
+            base_txt = f'{self.base}'
+            if self.base == np.e:
+                base_txt = 'e'
+
+            if self.mathtex:
+                fmt_parts = (f'${base_txt}^', '{{{e}}}$')
+            else:
+                fmt_parts = (f'{base_txt}^', '{e}')
+
+            fmt = ''.join(fmt_parts)
+            exps = [_exp(num, self.base) for num in x]
+            labels = [fmt.format(e=e) for e in exps]
+            return labels
 
 
 class date_format:

diff --git a/mizani/tests/test_formatters.py b/mizani/tests/test_formatters.py
@@ -100,23 +100,15 @@ def test_log_format():
     assert formatter([1, 35, 60, 1e6]) == ['1', '4e1', '6e1', '1e6']
 
     formatter = log_format(base=2)
-    assert formatter([1, 2, 4, 8]) == ['1', '10', '100', '1000']
-    assert formatter([0b1, 0b10, 0b11, 0b1011]) == ['1', '10', '11', '1011']
+    assert formatter([1, 2, 4, 8]) == ['2^0', '2^1', '2^2', '2^3']
+    assert formatter([0b1, 0b10, 0b11]) == ['2^0', '2^1', '2^1.585']
 
     formatter = log_format(base=8)
-    assert formatter([1, 4, 8, 16, 64]) == ['1', '4', '10', '20', '100']
+    assert formatter([1, 4, 8, 64]) == ['8^0', '8^0.667', '8^1', '8^2']
 
-    formatter = log_format(base=16)
-    assert formatter([1, 8, 16, 32, 256]) == ['1', '8', '10', '20', '100']
-
-    # Floats
-    formatter = log_format(base=8)
-    assert formatter([1., 4., 8., 16.]) == ['1', '4', '10', '20']
-
-    # Fallback to base 10
     formatter = log_format(base=np.e)
-    with pytest.warns(UserWarning, match=r"base = 10$"):
-        assert formatter([1, 8, 16, 32]) == ['1', '8', '16', '32']
+    assert formatter([1, np.pi, np.e**2, np.e**3]) == \
+        ['e^0', 'e^1.145', 'e^2', 'e^3']
 
     # mathtex
     formatter = log_format(mathtex=True)
@@ -125,6 +117,9 @@ def test_log_format():
     assert formatter([35, 60]) == ['35', '60']
     assert formatter([1, 10000]) == ['$10^{0}$', '$10^{4}$']
 
+    formatter = log_format(base=8, mathtex=True)
+    assert formatter([1, 4, 64]) == ['$8^{0}$', '$8^{0.667}$', '$8^{2}$']
+
 
 def test_date_format():
     x = pd.date_range('1/1/2010', periods=4, freq='4AS')