fix(geometry): is_clockwise() now works as expected for a disv problem (

#1374)

* fix(geometry): is_clockwise() now works as expected for a disv problem
* new test asserts a failure for a counter-clockwise set of vertices.  Ran black on new test script

autotest/t081_test_is_clockwise.py

@@ -0,0 +1,31 @@
+import flopy
+import numpy as np
+
+
+def test_does_isclockwise_work():
+    # Create some points
+    verts = []
+    verts.append([0, 20.0000, 30.0000])
+    verts.append([1, 18.9394, 25.9806])
+    verts.append([2, 21.9192, 25.3013])
+    verts.append([3, 22.2834, 27.5068])
+
+    # List the points above in counter-clockwise order
+    iv = [0, 0, 1, 2, 3]
+
+    # Organize the previous info into lists of x an y data
+    xv, yv = [], []
+    xyverts = []
+    for v in iv[1:]:
+        tiv, txv, tyv = verts[v]
+        xv.append(txv)
+        yv.append(tyv)
+
+    # is_clockwise() should fail and return false
+    rslt = flopy.utils.geometry.is_clockwise(xv, yv)
+
+    assert bool(rslt) is False, "is_clockwise() failed"
+
+
+if __name__ == "__main__":
+    test_does_isclockwise_work()

flopy/utils/geometry.py

@@ -827,10 +827,10 @@ def is_clockwise(*geom):
         geom = GeoSpatialUtil(geom, shapetype="Polygon")
         x, y = np.array(geom.points[0]).T
 
-    if not (x[0] == x[-1]) and (y[0] == y[-1]):
+    if not ((x[0] == x[-1]) and (y[0] == y[-1])):
         # close the ring if needed
-        x = np.append(x, x[-1])
-        y = np.append(y, y[-1])
+        x = np.append(x, x[0])
+        y = np.append(y, y[0])
     return np.sum((np.diff(x)) * (y[1:] + y[:-1])) > 0