Remove support for non-1D errorbars.

doc/api/api_changes_3.3/removals.rst

@@ -221,6 +221,8 @@ Arguments
 - `.MaxNLocator.set_params()` no longer accepts arbitrary keyword arguments.
 - `~.Axes.pie` no longer accepts and squeezes non-1D inputs; pass 1D input to
   the ``x`` argument.
+- Passing (n, 1)-shaped error arrays to `.Axes.errorbar()` is no longer
+  supported; pass a 1D array instead.
 
 rcParams
 ~~~~~~~~

lib/matplotlib/axes/_axes.py

@@ -3368,7 +3368,7 @@ def xywhere(xs, ys, mask):
             ys = [thisy for thisy, b in zip(ys, mask) if b]
             return xs, ys
 
-        def extract_err(err, data):
+        def extract_err(name, err, data):
             """
             Private function to parse *err* and subtract/add it to *data*.
 
@@ -3380,20 +3380,9 @@ def extract_err(err, data):
                 iter(b)
             except (TypeError, ValueError):
                 a = b = err  # Symmetric error: 1D iterable.
-            # This could just be `np.ndim(a) > 1 and np.ndim(b) > 1`, except
-            # for the (undocumented, but tested) support for (n, 1) arrays.
-            a_sh = np.shape(a)
-            b_sh = np.shape(b)
-            if (len(a_sh) > 2 or (len(a_sh) == 2 and a_sh[1] != 1)
-                    or len(b_sh) > 2 or (len(b_sh) == 2 and b_sh[1] != 1)):
+            if np.ndim(a) > 1 or np.ndim(b) > 1:
                 raise ValueError(
-                    "err must be a scalar or a 1D or (2, n) array-like")
-            if len(a_sh) == 2 or len(b_sh) == 2:
-                cbook.warn_deprecated(
-                    "3.1", message="Support for passing a (n, 1)-shaped error "
-                    "array to errorbar() is deprecated since Matplotlib "
-                    "%(since)s and will be removed %(removal)s; pass a 1D "
-                    "array instead.")
+                    f"{name}err must be a scalar or a 1D or (2, n) array-like")
             # Using list comprehensions rather than arrays to preserve units.
             for e in [a, b]:
                 if len(data) != len(e):
@@ -3405,7 +3394,7 @@ def extract_err(err, data):
             return low, high
 
         if xerr is not None:
-            left, right = extract_err(xerr, x)
+            left, right = extract_err('x', xerr, x)
             # select points without upper/lower limits in x and
             # draw normal errorbars for these points
             noxlims = ~(xlolims | xuplims)
@@ -3454,7 +3443,7 @@ def extract_err(err, data):
                                                   **eb_cap_style))
 
         if yerr is not None:
-            lower, upper = extract_err(yerr, y)
+            lower, upper = extract_err('y', yerr, y)
             # select points without upper/lower limits in y and
             # draw normal errorbars for these points
             noylims = ~(lolims | uplims)

lib/matplotlib/tests/test_axes.py

@@ -2855,9 +2855,7 @@ def test_errorbar():
     # Now switch to a more OO interface to exercise more features.
     fig, axs = plt.subplots(nrows=2, ncols=2, sharex=True)
     ax = axs[0, 0]
-    # Try a Nx1 shaped error just to check
-    with pytest.warns(MatplotlibDeprecationWarning):
-        ax.errorbar(x, y, yerr=np.reshape(yerr, (len(y), 1)), fmt='o')
+    ax.errorbar(x, y, yerr=yerr, fmt='o')
     ax.set_title('Vert. symmetric')
 
     # With 4 subplots, reduce the number of axis ticks to avoid crowding.
@@ -4754,10 +4752,8 @@ def generate_errorbar_inputs():
                                 [1, 1, 1, 1, 1],
                                 [[1, 1, 1, 1, 1],
                                  [1, 1, 1, 1, 1]],
-                                [[1]] * 5,
                                 np.ones(5),
                                 np.ones((2, 5)),
-                                np.ones((5, 1)),
                                 None
                                 ])
     xerr_cy = cycler('xerr', err_cycler)
@@ -4774,11 +4770,9 @@ def generate_errorbar_inputs():
 
 @pytest.mark.parametrize('kwargs', generate_errorbar_inputs())
 def test_errorbar_inputs_shotgun(kwargs):
-    # (n, 1)-shaped error deprecation already tested by test_errorbar.
-    with mpl.cbook._suppress_matplotlib_deprecation_warning():
-        ax = plt.gca()
-        eb = ax.errorbar(**kwargs)
-        eb.remove()
+    ax = plt.gca()
+    eb = ax.errorbar(**kwargs)
+    eb.remove()
 
 
 @image_comparison(["dash_offset"], remove_text=True)