Support string-type parametric coordinates

proplot/axes/base.py

@@ -1360,7 +1360,11 @@ def parametric(
         *args : (y,), (x, y), or (x, y, c)
             The coordinates. If `x` is not provided, it is inferred from `y`.
             The parametric coordinate can be indicated as a third positional
-            argument or with the `c` or `values` keywords.
+            argument or with the `c`, `values`, or `labels` keywords. The
+            parametric coordinate can be numeric or an array of string labels.
+        c, values, labels : array-like, optional
+            The parametric coordinates passed as a keyword argument. They
+            can also be passed as a third positional argument.
         %(axes.cmap_norm)s
         interp : int, optional
             If greater than ``0``, we interpolate to additional points

proplot/axes/plot.py

@@ -671,6 +671,7 @@ def _parse_string_coords(*args, which='x', **kwargs):
     # correspond to indices while the latter can mysteriously truncate labels.
     res = []
     for arg in args:
+        arg = _to_arraylike(arg)
         if _is_string(arg) and arg.ndim > 1:
             raise ValueError('Non-1D string coordinate input is unsupported.')
         if not _is_string(arg):
@@ -749,7 +750,9 @@ def _auto_format_1d(
         if not nocycle:
             kwargs['labels'] = _to_ndarray(labels)
         elif parametric:
-            kwargs['values'] = _to_ndarray(labels)
+            values, colorbar_kw = _parse_string_coords(labels, which='')
+            kwargs['values'] = _to_ndarray(values)
+            kwargs.setdefault('colorbar_kw', {}).update(colorbar_kw)
 
     # The basic x and y settings
     if not projection: