Pass dual axis arguments through Scale again

Author: lukelbd

docs/axis.py

@@ -523,9 +523,8 @@
     xformatter='null', ylabel='pressure (hPa)',
     ylim=(1000, 10), xlocator=[], ycolor=c1, gridcolor=c1
 )
-scale = plot.Scale('height')
 ax.dualy(
-    scale, label='height (km)', ticks=2.5, color=c2, gridcolor=c2, grid=True
+    'height', label='height (km)', ticks=2.5, color=c2, gridcolor=c2, grid=True
 )
 
 # Height as the linear scale, pressure on opposite axis (scale height 7km)
@@ -534,9 +533,8 @@
     xformatter='null', ylabel='height (km)', ylim=(0, 20), xlocator='null',
     grid=True, gridcolor=c2, ycolor=c2
 )
-scale = plot.Scale('pressure')
 ax.dualy(
-    scale, label='pressure (hPa)', locator=100, color=c1, gridcolor=c1, grid=True,
+    'pressure', label='pressure (hPa)', locator=100, color=c1, gridcolor=c1, grid=True,
 )
 plot.rc.reset()
 
@@ -557,13 +555,12 @@
 ax.plot(x, response, color=c1, lw=2)
 
 # Add inverse scale to top
-scale = plot.Scale('inverse')
 ax.format(
     xlabel='wavenumber (days$^{-1}$)', ylabel='response', grid=False,
     title='Imaginary response function',
     suptitle='Duplicate axes with wavenumber and period',
 )
 ax = ax.dualx(
-    scale, locator='log', locator_kw={'subs': (1, 2, 5)}, label='period (days)'
+    'inverse', locator='log', locator_kw={'subs': (1, 2, 5)}, label='period (days)'
 )
 plot.rc.reset()

proplot/axes/cartesian.py

@@ -78,12 +78,13 @@
 
 Parameters
 ----------
-arg : function, (function, function), or `~matplotlib.scale.ScaleBase`
+arg : function, (function, function), or scale-spec
     Used to transform units from the parent axis to the secondary axis.
     This can be a `~proplot.scale.FuncScale` itself or a function,
-    (function, function) tuple, or `~matplotlib.scale.ScaleBase` instance used
-    to *generate* a `~proplot.scale.FuncScale` (see
-    `~proplot.scale.FuncScale` for details).
+    (function, function) tuple, or an axis scale specification interpreted
+    by the `~proplot.constructor.Scale` constructor function, any of which will
+    be used to build a `~proplot.scale.FuncScale` and applied to the dual axis
+    (see `~proplot.scale.FuncScale` for details).
 {args} : optional
     Prepended with ``'{x}'`` and passed to `Axes.format`.
 """

proplot/scale.py

@@ -281,14 +281,12 @@ def __init__(
               ``ax.dual%(x)s((lambda x: x**2, lambda x: x**0.5))``.
               Again, if the first function is linear or involutory, you do
               not need to provide the second!
-            * A `~matplotlib.scale.ScaleBase` instance, e.g. a scale returned
-              by the `~proplot.constructor.Scale` constructor function. The
-              forward transformation, inverse transformation, and default axis
-              locators and formatters are borrowed from the resulting scale
-              class.  For example, to apply the inverse, use
-              ``ax.dual%(x)s(plot.Scale('inverse'))``.
-              To apply the base-10 exponential function, use
-              ``ax.dual%(x)s(plot.Scale('exp', 10))``.
+            * A scale specification interpreted by the `~proplot.constructor.Scale`
+              constructor function. The forward transformation, inverse transformation,
+              and default axis locators and formatters are borrowed from the resulting
+              `~matplotlib.scale.ScaleBase` instance. For example, to apply the
+              inverse, use ``ax.dual%(x)s('inverse')``. To apply the base-10
+              exponential function, use ``ax.dual%(x)s(('exp', 10))``.
 
         invert : bool, optional
             If ``True``, the forward and inverse functions are *swapped*.
@@ -316,16 +314,18 @@ def __init__(
             forward = inverse = arg
         elif np.iterable(arg) and len(arg) == 2 and all(map(callable, arg)):
             forward, inverse = arg
-        elif isinstance(arg, mscale.ScaleBase):
-            trans = arg.get_transform()
+        else:
+            from .constructor import Scale
+            try:
+                scale = Scale(arg)
+            except ValueError:
+                raise ValueError(
+                    'Input should be a function, 2-tuple of forward and and inverse '
+                    f'functions, or an axis scale specification, not {arg!r}.'
+                )
+            trans = scale.get_transform()
             forward = trans.transform
             inverse = trans.inverted().transform
-        else:
-            raise ValueError(
-                'Input should be a function, 2-tuple of forward and '
-                'and inverse functions, or a matplotlib.scale.ScaleBase '
-                f'instance, not {arg!r}.'
-            )
 
         # Create the FuncTransform or composite transform used for this class
         # May need to invert functions for dualx() and dualy()