matplotlib · schtandard · Mar 15, 2026 · Mar 16, 2026 · Mar 16, 2026 · Mar 16, 2026
diff --git a/lib/matplotlib/mpl-data/matplotlibrc b/lib/matplotlib/mpl-data/matplotlibrc
@@ -414,6 +414,9 @@
                                      # will be used when it can remove
                                      # at least this number of significant
                                      # digits from tick labels.
+#axes.formatter.legacy_symlog_ticker: True # Use legacy tick placement algorithm
+                                           # for symlog axes. May cause bad tick
+                                           # placement in some cases.
 
 #axes.spines.left:   True  # display axis spines
 #axes.spines.bottom: True

diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -1156,6 +1156,7 @@ def _convert_validator_spec(key, conv):
     "axes.formatter.min_exponent": validate_int,
     "axes.formatter.useoffset": validate_bool,
     "axes.formatter.offset_threshold": validate_int,
+    "axes.formatter.legacy_symlog_ticker": validate_bool,
     "axes.unicode_minus": validate_bool,
     # This entry can be either a cycler object or a string repr of a
     # cycler-object, which gets eval()'ed to create the object.
@@ -2014,6 +2015,13 @@ class _Param:
                     "remove at least this number of significant digits from tick "
                     "labels."
     ),
+    _Param(
+        "axes.formatter.legacy_symlog_ticker",
+        default=True,
+        validator=validate_bool,
+        description="When True, ticks in symlog axes are placed using legacy rules. "
+                    "This is known to cause badly labeled axes in some cases."
+    ),
     _Param(
         "axes.spines.left",
         default=True,

diff --git a/lib/matplotlib/scale.py b/lib/matplotlib/scale.py
@@ -539,7 +539,7 @@ class SymmetricalLogScale(ScaleBase):
     name = 'symlog'
 
     @_make_axis_parameter_optional
-    def __init__(self, axis=None, *, base=10, linthresh=2, subs=None, linscale=1):
+    def __init__(self, axis=None, *, base=10, linthresh=2, subs='auto', linscale=1):
         self._transform = SymmetricalLogTransform(base, linthresh, linscale)
         self.subs = subs
 
@@ -553,7 +553,9 @@ def set_default_locators_and_formatters(self, axis):
         axis.set_major_formatter(LogFormatterSciNotation(self.base))
         axis.set_minor_locator(SymmetricalLogLocator(self.get_transform(),
                                                      self.subs))
-        axis.set_minor_formatter(NullFormatter())
+        axis.set_minor_formatter(
+            LogFormatterSciNotation(self.base,
+                                    labelOnlyBase=(self.subs != 'auto')))
 
     def get_transform(self):
         """Return the `.SymmetricalLogTransform` associated with this scale."""

diff --git a/lib/matplotlib/scale.pyi b/lib/matplotlib/scale.pyi
@@ -112,7 +112,7 @@ class SymmetricalLogScale(ScaleBase):
         *,
         base: float = ...,
         linthresh: float = ...,
-        subs: Iterable[int] | None = ...,
+        subs: Iterable[int] | Literal["auto", "all"] | None = ...,
         linscale: float = ...
     ) -> None: ...
     @property

diff --git a/lib/matplotlib/tests/baseline_images/test_axes/symlog2_nolegacy.pdf b/lib/matplotlib/tests/baseline_images/test_axes/symlog2_nolegacy.pdf
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/symlog_nolegacy.pdf b/lib/matplotlib/tests/baseline_images/test_axes/symlog_nolegacy.pdf
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -1341,11 +1341,9 @@ def test_fill_between_interpolate_nan():
                     interpolate=True, alpha=0.5)
 
 
-# test_symlog and test_symlog2 used to have baseline images in all three
-# formats, but the png and svg baselines got invalidated by the removal of
-# minor tick overstriking.
-@image_comparison(['symlog.pdf'])
+@image_comparison(['symlog_nolegacy.pdf'])
 def test_symlog():
+    mpl.rcParams['axes.formatter.legacy_symlog_ticker'] = False
     x = np.array([0, 1, 2, 4, 6, 9, 12, 24])
     y = np.array([1000000, 500000, 100000, 100, 5, 0, 0, 0])
 
@@ -1356,8 +1354,36 @@ def test_symlog():
     ax.set_ylim(-1, 10000000)
 
 
-@image_comparison(['symlog2.pdf'], remove_text=True)
+@image_comparison(['symlog2_nolegacy.pdf'], remove_text=True)
 def test_symlog2():
+    mpl.rcParams['axes.formatter.legacy_symlog_ticker'] = False
+    # Numbers from -50 to 50, with 0.1 as step
+    x = np.arange(-50, 50, 0.001)
+
+    fig, axs = plt.subplots(5, 1)
+    for ax, linthresh in zip(axs, [20., 2., 1., 0.1, 0.01]):
+        ax.plot(x, x)
+        ax.set_xscale('symlog', linthresh=linthresh)
+        ax.grid(True)
+    axs[-1].set_ylim(-0.1, 0.1)
+
+
+@image_comparison(['symlog.pdf'])
+def test_legacy_symlog():
+    mpl.rcParams['axes.formatter.legacy_symlog_ticker'] = True
+    x = np.array([0, 1, 2, 4, 6, 9, 12, 24])
+    y = np.array([1000000, 500000, 100000, 100, 5, 0, 0, 0])
+
+    fig, ax = plt.subplots()
+    ax.plot(x, y)
+    ax.set_yscale('symlog')
+    ax.set_xscale('linear')
+    ax.set_ylim(-1, 10000000)
+
+
+@image_comparison(['symlog2.pdf'], remove_text=True)
+def test_legacy_symlog2():
+    mpl.rcParams['axes.formatter.legacy_symlog_ticker'] = True
     # Numbers from -50 to 50, with 0.1 as step
     x = np.arange(-50, 50, 0.001)
 

diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -608,12 +608,62 @@ def test_set_params(self):
 class TestSymmetricalLogLocator:
     def test_set_params(self):
         """
-        Create symmetrical log locator with default subs =[1.0] numticks = 15,
+        Create symmetrical log locator with default subs=[1.0] numticks='auto',
         and change it to something else.
         See if change was successful.
         Should not exception.
         """
-        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1)
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            legacy_symlog_ticker=False)
+        sym.set_params(subs=[2.0], numticks=8)
+        assert sym._subs == [2.0]
+        assert sym.numticks == 8
+
+    @pytest.mark.parametrize(
+            'vmin, vmax, expected',
+            [
+                (0, 1, [-1, 0, 1, 10]),
+                (-1, 1, [-10, -1, 0, 1, 10]),
+            ],
+    )
+    def test_values(self, vmin, vmax, expected):
+        # https://github.com/matplotlib/matplotlib/issues/25945
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            legacy_symlog_ticker=False)
+        ticks = sym.tick_values(vmin=vmin, vmax=vmax)
+        assert_array_equal(ticks, expected)
+
+    def test_subs(self):
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            subs=[2.0, 4.0], legacy_symlog_ticker=False)
+        sym.create_dummy_axis()
+        sym.axis.set_view_interval(-10, 10)
+        assert_array_equal(sym(), [-400, -200, -40, -20, -4, -2, -0.4, -0.2, -0.1,
+                                   0.1, 0.2, 0.4, 2, 4, 20, 40, 200, 400])
+
+    def test_extending(self):
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            legacy_symlog_ticker=False)
+        sym.create_dummy_axis()
+        sym.axis.set_view_interval(8, 9)
+        assert_array_equal(sym(), [1, 10])
+        sym.axis.set_view_interval(8, 12)
+        assert_array_equal(sym(), [1, 10, 100])
+        assert sym.view_limits(10, 10) == (1, 100)
+        assert sym.view_limits(-10, -10) == (-100, -1)
+        assert sym.view_limits(0, 0) == (-1, 1)
+
+
+class TestLegacySymmetricalLogLocator:
+    def test_set_params(self):
+        """
+        Create symmetrical log locator with default subs=[1.0] numticks='auto',
+        and change it to something else.
+        See if change was successful.
+        Should not exception.
+        """
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            legacy_symlog_ticker=True)
         sym.set_params(subs=[2.0], numticks=8)
         assert sym._subs == [2.0]
         assert sym.numticks == 8
@@ -627,26 +677,29 @@ def test_set_params(self):
     )
     def test_values(self, vmin, vmax, expected):
         # https://github.com/matplotlib/matplotlib/issues/25945
-        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1)
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            legacy_symlog_ticker=True)
         ticks = sym.tick_values(vmin=vmin, vmax=vmax)
         assert_array_equal(ticks, expected)
 
     def test_subs(self):
-        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, subs=[2.0, 4.0])
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            subs=[2.0, 4.0], legacy_symlog_ticker=True)
         sym.create_dummy_axis()
         sym.axis.set_view_interval(-10, 10)
-        assert_array_equal(sym(), [-20, -40, -2, -4, 0, 2, 4, 20, 40])
+        assert_array_equal(sym(), [-10, -1, 0, 1, 10])
 
     def test_extending(self):
-        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1)
+        sym = mticker.SymmetricalLogLocator(base=10, linthresh=1, linscale=1,
+                                            legacy_symlog_ticker=True)
         sym.create_dummy_axis()
         sym.axis.set_view_interval(8, 9)
         assert (sym() == [1.0]).all()
         sym.axis.set_view_interval(8, 12)
         assert (sym() == [1.0, 10.0]).all()
         assert sym.view_limits(10, 10) == (1, 100)
         assert sym.view_limits(-10, -10) == (-100, -1)
-        assert sym.view_limits(0, 0) == (-0.001, 0.001)
+        assert sym.view_limits(0, 0) == (-1, 1)
 
 
 class TestAsinhLocator: