all in one change

pandas/plotting/_core.py

@@ -308,10 +308,21 @@ def _setup_subplots(self):
 
         axes = _flatten(axes)
 
-        if self.logx or self.loglog:
+        valid_log = [False, True, 'sym', None]
+
+        for i in (self.logx, self.logy, self.loglog):
+            if i not in valid_log:
+                raise ValueError("Valid inputs are boolean, None and 'sym'.")
+
+        if self.logx is True or self.loglog is True:
             [a.set_xscale('log') for a in axes]
-        if self.logy or self.loglog:
+        elif self.logx == 'sym' or self.loglog == 'sym':
+            [a.set_xscale('symlog') for a in axes]
+
+        if self.logy is True or self.loglog is True:
             [a.set_yscale('log') for a in axes]
+        elif self.logy == 'sym' or self.loglog == 'sym':
+            [a.set_yscale('symlog') for a in axes]
 
         self.fig = fig
         self.axes = axes

pandas/tests/plotting/test_frame.py

@@ -231,14 +231,32 @@ def test_plot_xy(self):
     @pytest.mark.slow
     def test_logscales(self):
         df = DataFrame({'a': np.arange(100)}, index=np.arange(100))
+
         ax = df.plot(logy=True)
         self._check_ax_scales(ax, yaxis='log')
+        assert ax.get_yscale() == 'log'
+
+        ax = df.plot(logy='sym')
+        self._check_ax_scales(ax, yaxis='symlog')
+        assert ax.get_yscale() == 'symlog'
 
         ax = df.plot(logx=True)
         self._check_ax_scales(ax, xaxis='log')
+        assert ax.get_xscale() == 'log'
+
+        ax = df.plot(logx='sym')
+        self._check_ax_scales(ax, xaxis='symlog')
+        assert ax.get_xscale() == 'symlog'
 
         ax = df.plot(loglog=True)
         self._check_ax_scales(ax, xaxis='log', yaxis='log')
+        assert ax.get_xscale() == 'log'
+        assert ax.get_yscale() == 'log'
+
+        ax = df.plot(loglog='sym')
+        self._check_ax_scales(ax, xaxis='symlog', yaxis='symlog')
+        assert ax.get_xscale() == 'symlog'
+        assert ax.get_yscale() == 'symlog'
 
     @pytest.mark.slow
     def test_xcompat(self):