matplotlib · tacaswell · Dec 23, 2015 · Dec 22, 2015 · Dec 22, 2015
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -33,6 +33,7 @@
 from matplotlib.markers import (
     CARETLEFT, CARETRIGHT, CARETUP, CARETDOWN,
     CARETLEFTBASE, CARETRIGHTBASE, CARETUPBASE, CARETDOWNBASE)
+from matplotlib import _path
 
 
 def segment_hits(cx, cy, x, y, radius):
@@ -702,9 +703,7 @@ def set_transform(self, t):
     def _is_sorted(self, x):
         """return True if x is sorted in ascending order"""
         # We don't handle the monotonically decreasing case.
-        if len(x) < 2:
-            return True
-        return np.nanmin(x[1:] - x[:-1]) >= 0
+        return _path.is_sorted(x)
 
     @allow_rasterization
     def draw(self, renderer):

diff --git a/lib/matplotlib/tests/test_lines.py b/lib/matplotlib/tests/test_lines.py
@@ -158,8 +158,9 @@ def test_marker_fill_styles():
 def test_nan_is_sorted():
     # Exercises issue from PR #2744 (NaN throwing warning in _is_sorted)
     line = mlines.Line2D([],[])
-    assert_true(line._is_sorted(np.array([1,2,3])))
-    assert_true(not line._is_sorted(np.array([1,np.nan,3])))
+    assert_true(line._is_sorted(np.array([1, 2, 3])))
+    assert_true(line._is_sorted(np.array([1, np.nan, 3])))
+    assert_true(not line._is_sorted([3, 5] + [np.nan] * 100 + [0, 2]))
 
 
 if __name__ == '__main__':

diff --git a/src/_path.h b/src/_path.h
@@ -1183,4 +1183,70 @@ int convert_to_string(PathIterator &path,
 
 }
 
+template<class T>
+struct _is_sorted
+{
+    bool operator()(PyArrayObject *array)
+    {
+        npy_intp size;
+        npy_intp i;
+        T last_value;
+        T current_value;
+
+        size = PyArray_DIM(array, 0);
+
+        for (i = 0; i < size; ++i) {
+            last_value = *((T *)PyArray_GETPTR1(array, i));
+            if (std::isfinite(last_value)) {
+                break;
+            }
+        }
+
+        if (i == size) {
+            // The whole array is non-finite
+            return false;
+        }
+
+        for (; i < size; ++i) {
+            current_value = *((T *)PyArray_GETPTR1(array, i));
+            if (std::isfinite(current_value)) {
+                if (current_value < last_value) {
+                    return false;
+                }
+                last_value = current_value;
+            }
+        }
+
+        return true;
+    }
+};
+
+
+template<class T>
+struct _is_sorted_int
+{
+    bool operator()(PyArrayObject *array)
+    {
+        npy_intp size;
+        npy_intp i;
+        T last_value;
+        T current_value;
+
+        size = PyArray_DIM(array, 0);
+
+        last_value = *((T *)PyArray_GETPTR1(array, 0));
+
+        for (i = 1; i < size; ++i) {
+            current_value = *((T *)PyArray_GETPTR1(array, i));
+            if (current_value < last_value) {
+                return false;
+            }
+            last_value = current_value;
+        }
+
+        return true;
+    }
+};
+
+
 #endif
diff --git a/src/_path_wrapper.cpp b/src/_path_wrapper.cpp
@@ -726,6 +726,91 @@ static PyObject *Py_convert_to_string(PyObject *self, PyObject *args, PyObject *
     return result;
 }
 
+
+const char *Py_is_sorted__doc__ = "is_sorted(array)\n\n"
+    "Returns True if 1-D array is monotonically increasing, ignoring NaNs\n";
+
+static PyObject *Py_is_sorted(PyObject *self, PyObject *obj)
+{
+    npy_intp size;
+    bool result;
+
+    PyArrayObject *array = (PyArrayObject *)PyArray_FromAny(
+        obj, NULL, 1, 1, 0, NULL);
+
+    if (array == NULL) {
+        return NULL;
+    }
+
+    size = PyArray_DIM(array, 0);
+
+    if (size < 2) {
+        Py_DECREF(array);
+        Py_RETURN_TRUE;
+    }
+
+    /* Handle just the most common types here, otherwise coerce to
+    double */
+    switch(PyArray_TYPE(array)) {
+    case NPY_INT:
+        {
+            _is_sorted_int<npy_int> is_sorted;
+            result = is_sorted(array);
+        }
+        break;
+
+    case NPY_LONG:
+        {
+            _is_sorted_int<npy_long> is_sorted;
+            result = is_sorted(array);
+        }
+        break;
+
+    case NPY_LONGLONG:
+        {
+            _is_sorted_int<npy_longlong> is_sorted;
+            result = is_sorted(array);
+        }
+        break;
+
+    case NPY_FLOAT:
+        {
+            _is_sorted<npy_float> is_sorted;
+            result = is_sorted(array);
+        }
+        break;
+
+    case NPY_DOUBLE:
+        {
+            _is_sorted<npy_double> is_sorted;
+            result = is_sorted(array);
+        }
+        break;
+
+    default:
+        {
+            Py_DECREF(array);
+            array = (PyArrayObject *)PyArray_FromObject(obj, NPY_DOUBLE, 1, 1);
+
+            if (array == NULL) {
+                return NULL;
+            }
+
+            _is_sorted<npy_double> is_sorted;
+            result = is_sorted(array);
+        }
+    }
+
+    Py_DECREF(array);
+
+    if (result) {
+        Py_RETURN_TRUE;
+    } else {
+        Py_RETURN_FALSE;
+    }
+}
+
+
 extern "C" {
 
     static PyMethodDef module_functions[] = {
@@ -745,6 +830,7 @@ extern "C" {
         {"convert_path_to_polygons", (PyCFunction)Py_convert_path_to_polygons, METH_VARARGS, Py_convert_path_to_polygons__doc__},
         {"cleanup_path", (PyCFunction)Py_cleanup_path, METH_VARARGS, Py_cleanup_path__doc__},
         {"convert_to_string", (PyCFunction)Py_convert_to_string, METH_VARARGS, Py_convert_to_string__doc__},
+        {"is_sorted", (PyCFunction)Py_is_sorted, METH_O, Py_is_sorted__doc__},
         {NULL}
     };