Backport PR #9723: ENH: Catch masked array and invalid x, y to pcolor…

…mesh
matplotlib · dstansby · Nov 14, 2017 · Nov 13, 2017 · Nov 13, 2017 · b3f0c28894f400d0345a8925c64875ec1dfcd049
commit b3f0c28894f400d0345a8925c64875ec1dfcd049
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -5172,7 +5172,21 @@ def _pcolorargs(funcname, *args, **kw):
            return X, Y, C

        if len(args) == 3:
-            X, Y, C = [np.asanyarray(a) for a in args]
+            # Check x and y for bad data...
+            C = np.asanyarray(args[2])
+            X, Y = [cbook.safe_masked_invalid(a) for a in args[:2]]
+            if funcname == 'pcolormesh':
+                if np.ma.is_masked(X) or np.ma.is_masked(Y):
+                    raise ValueError(
+                        'x and y arguments to pcolormesh cannot have '
+                        'non-finite values or be of type '
+                        'numpy.ma.core.MaskedArray with masked values')
+                # safe_masked_invalid() returns an ndarray for dtypes other
+                # than floating point.
+                if isinstance(X, np.ma.core.MaskedArray):
+                    X = X.data  # strip mask as downstream doesn't like it...
+                if isinstance(Y, np.ma.core.MaskedArray):
+                    Y = Y.data
            numRows, numCols = C.shape
        else:
            raise TypeError(
@@ -5567,7 +5581,6 @@ def pcolormesh(self, *args, **kwargs):
        # convert to one dimensional arrays
        C = C.ravel()
        coords = np.column_stack((X, Y)).astype(float, copy=False)
-
        collection = mcoll.QuadMesh(Nx - 1, Ny - 1, coords,
                                    antialiased=antialiased, shading=shading,
                                    **kwargs)

diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -1150,6 +1150,12 @@ def test_pcolorargs():
        ax.pcolormesh(x, y, Z[:-1, :-1], shading="gouraud")
    with pytest.raises(TypeError):
        ax.pcolormesh(X, Y, Z[:-1, :-1], shading="gouraud")
+    x[0] = np.NaN
+    with pytest.raises(ValueError):
+        ax.pcolormesh(x, y, Z[:-1, :-1])
+    x = np.ma.array(x, mask=(x < 0))
+    with pytest.raises(ValueError):
+        ax.pcolormesh(x, y, Z[:-1, :-1])


 @image_comparison(baseline_images=['canonical'])