Changeset 775 in lmdz_wrf for trunk/tools

Timestamp:

May 25, 2016, 5:09:32 PM (9 years ago)

Author:

lfita

Message:

Adding `PolyArea?' Function to compute the area of the polygon following 'Shoelace formula'

File:

• trunk/tools/generic_tools.py (modified) (2 diffs)

trunk/tools/generic_tools.py

@@ -17 +17 @@
 fillValueF64 = 1.e20
 fillValueI32 = -99999
+
+####### Content
+# PolyArea: Function to compute the area of the polygon following 'Shoelace formula'
 
 def values_line(line, splitv, chars):
@@ -6229 +6232 @@
 
     return ilatlon, mindiffLl
+
+def PolyArea(x,y):
+    """ Function to compute the area of the polygon following 'Shoelace formula'
+      from: http://stackoverflow.com/questions/24467972/calculate-area-of-polygon-given-x-y-coordinates
+      x: x-values of the vertexs of the polygon
+      y: y-values of the vertexs of the polygon
+    >>> x = np.array([-0.5,0.5,0.5,-0.5])
+    >>> y = np.array([0.5,0.5,-0.5,-0.5])
+    >>> PolyArea(x,y)
+    1.0
+    """
+    return 0.5*np.abs(np.dot(x,np.roll(y,1))-np.dot(y,np.roll(x,1)))
+