Individual hatching styles for stackplot, as per Issue 27146

nbarlowATI · nbarlowATI · commit 914b213b5ce7 · 2023-10-31T13:50:40.000Z
diff --git a/doc/users/next_whats_new/stackplot_hatch.rst b/doc/users/next_whats_new/stackplot_hatch.rst
@@ -0,0 +1,27 @@
+``hatch`` parameter for stackplot
+-------------------------------------------
+
+The `~.Axes.stackplot` *hatch* parameter now accepts a list of strings describing hatching styles that will be applied sequentially to the layers in the stack:
+
+.. plot::
+    :include-source: true
+    :alt: Two charts, identified as ax1 and ax2, showing "stackplots", i.e. one-dimensional distributions of data stacked on top of one another. The first plot, ax1 has cross-hatching on all slices, having been given a single string as the "hatch" argument. The second plot, ax2 has different styles of hatching on each slice - diagonal hatching in opposite directions on the first two slices, cross-hatching on the third slice, and open circles on the fourth.
+
+    import matplotlib.pyplot as plt
+    fig, (ax1, ax2) = plt.subplots(ncols=2, figsize=(10,5))
+
+    cols = 10
+    rows = 4
+    data = (
+    np.reshape(np.arange(0, cols, 1), (1, -1)) ** 2
+    + np.reshape(np.arange(0, rows), (-1, 1))
+    + np.random.random((rows, cols))*5
+    )
+    x = range(data.shape[1])
+    ax1.stackplot(x, data, hatch="x")
+    ax2.stackplot(x, data, hatch=["//","\\","x","o"])
+
+    ax1.set_title("hatch='x'")
+    ax2.set_title("hatch=['//','\\\\','x','o']")
+
+    plt.show()
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -3792,12 +3792,15 @@ def spy(
 
 # Autogenerated by boilerplate.py.  Do not edit as changes will be lost.
 @_copy_docstring_and_deprecators(Axes.stackplot)
-def stackplot(x, *args, labels=(), colors=None, baseline="zero", data=None, **kwargs):
+def stackplot(
+    x, *args, labels=(), colors=None, hatch=None, baseline="zero", data=None, **kwargs
+):
     return gca().stackplot(
         x,
         *args,
         labels=labels,
         colors=colors,
+        hatch=hatch,
         baseline=baseline,
         **({"data": data} if data is not None else {}),
         **kwargs,
diff --git a/lib/matplotlib/stackplot.py b/lib/matplotlib/stackplot.py
@@ -16,7 +16,7 @@
 
 
 def stackplot(axes, x, *args,
-              labels=(), colors=None, baseline='zero',
+              labels=(), colors=None, hatch=None, baseline='zero',
               **kwargs):
     """
     Draw a stacked area plot.
@@ -55,6 +55,15 @@ def stackplot(axes, x, *args,
 
         If not specified, the colors from the Axes property cycle will be used.
 
+    hatch : list of str, default: None
+        A sequence of hatching styles.  See
+        :doc:`/gallery/shapes_and_collections/hatch_style_reference`.
+        The sequence will be cycled through for filling the
+        stacked areas from bottom to top.
+        It need not be exactly the same length as the number
+        of provided *y*, in which case the styles will repeat from the
+        beginning.
+
     data : indexable object, optional
         DATA_PARAMETER_PLACEHOLDER
 
@@ -76,6 +85,11 @@ def stackplot(axes, x, *args,
     else:
         colors = (axes._get_lines.get_next_color() for _ in y)
 
+    if hatch is None or isinstance(hatch, str):
+        hatch = itertools.cycle([hatch])
+    else:
+        hatch = itertools.cycle(hatch)
+
     # Assume data passed has not been 'stacked', so stack it here.
     # We'll need a float buffer for the upcoming calculations.
     stack = np.cumsum(y, axis=0, dtype=np.promote_types(y.dtype, np.float32))
@@ -113,7 +127,9 @@ def stackplot(axes, x, *args,
 
     # Color between x = 0 and the first array.
     coll = axes.fill_between(x, first_line, stack[0, :],
-                             facecolor=next(colors), label=next(labels, None),
+                             facecolor=next(colors),
+                             hatch=next(hatch),
+                             label=next(labels, None),
                              **kwargs)
     coll.sticky_edges.y[:] = [0]
     r = [coll]
@@ -122,6 +138,7 @@ def stackplot(axes, x, *args,
     for i in range(len(y) - 1):
         r.append(axes.fill_between(x, stack[i, :], stack[i + 1, :],
                                    facecolor=next(colors),
+                                   hatch=next(hatch),
                                    label=next(labels, None),
                                    **kwargs))
     return r
diff --git a/lib/matplotlib/stackplot.pyi b/lib/matplotlib/stackplot.pyi
@@ -12,6 +12,7 @@ def stackplot(
     *args: ArrayLike,
     labels: Iterable[str] = ...,
     colors: Iterable[ColorType] | None = ...,
+    hatch: Iterable[str] | str | None = ...,
     baseline: Literal["zero", "sym", "wiggle", "weighted_wiggle"] = ...,
     **kwargs
 ) -> list[PolyCollection]: ...
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -3084,6 +3084,27 @@ def layers(n, m):
     axs[1, 1].stackplot(range(100), d.T, baseline='weighted_wiggle')
 
 
+@check_figures_equal()
+def test_stackplot_hatching(fig_ref, fig_test):
+    x = np.linspace(0, 10, 10)
+    y1 = 1.0 * x
+    y2 = 2.0 * x + 1
+    y3 = 3.0 * x + 2
+    # stackplot with different hatching styles (issue #27146)
+    ax_test = fig_test.subplots()
+    ax_test.stackplot(x, y1, y2, y3, hatch=["x", "//", "\\\\"], colors=["white"])
+    ax_test.set_xlim((0, 10))
+    ax_test.set_ylim((0, 70))
+    # compare with result from hatching each layer individually
+    stack_baseline = np.zeros(len(x))
+    ax_ref = fig_ref.subplots()
+    ax_ref.fill_between(x, stack_baseline, y1, hatch="x", facecolor="white")
+    ax_ref.fill_between(x, y1, y1+y2, hatch="//", facecolor="white")
+    ax_ref.fill_between(x, y1+y2, y1+y2+y3, hatch="\\\\", facecolor="white")
+    ax_ref.set_xlim((0, 10))
+    ax_ref.set_ylim((0, 70))
+
+
 def _bxp_test_helper(
         stats_kwargs={}, transform_stats=lambda s: s, bxp_kwargs={}):
     np.random.seed(937)
