converting degrees to u,v and u,v to deg

xbTools/general/deg2uv.py

@@ -0,0 +1,102 @@
+# -*- coding: utf-8 -*-
+"""
+--- Synopsis --- 
+This script converts degrees to u,v vectors. Intensity of a parameter can be included to scale the vectors for quiver plots.
+
+--- Remarks --- 
+See also: 
+To-Do: 
+Dependencies: 
+
+--- Version --- 
+Created on Fri October 05 16:34:50 2018
+@author: BEMC
+Project: general
+Script name: deg2uv.py 
+
+--- Revision --- 
+To-Do Subversioncontrol 
+Status: Unverified 
+
+Witteveen+Bos Consulting Engineers 
+Van Twickelostraat 2 
+P.O. box 233 
+7400 AE Deventer 
+The Netherlands 
+	
+	Give an array of directions will return the U and V
+	components. intensity is optional.
+	
+"""
+# 1. Import modules 
+import numpy as np 
+
+# 2. Define new functions 
+def deg2uv(direction,intensity=np.nan):
+    """
+    Function converts degrees to vector, denoted as
+    u and v
+    
+    Parameters
+    ----------
+    direction : numpy array
+        direction in degrees in numpy array.
+    intensity : numpy array
+        length of the vector. The default is np.nan. and 1 will be used
+
+    Returns
+    -------
+    u : np array
+        magnitude in x direction
+    v : np array
+        magnitude in y direction
+
+    """
+    Dir_nan_index = np.isnan(direction)
+
+    # Make nan 0 to perform sin cos operations
+    Dir_0 = direction
+    if np.any(Dir_nan_index):
+        Dir_0[Dir_nan_index] = 0
+        intensity[Dir_nan_index] = 0
+
+    rad = -4.0*np.arctan(1.0)/180.
+
+    if ~np.all(np.isnan(intensity)):
+        u   = intensity*np.sin(Dir_0*rad)
+        v   = -intensity*np.cos(Dir_0*rad)
+    else:
+        u   = np.sin(Dir_0*rad)
+        v   = -np.cos(Dir_0*rad)
+
+    # Replace all original nan with nan
+    #u[Dir_nan_index] = np.nan
+    #v[Dir_nan_index] = np.nan
+    return u,v
+
+def uv2deg(u,v,convention):
+    """
+    Function converts u,v vector to direction, denoted as
+    direction
+    
+    Parameters
+    ----------
+    u : numpy array
+        x-component (e.g. velocity).
+    v : numpy array
+        y-component (e.g. velocity)
+    convention: nautical or cartesian
+
+    Returns
+    -------
+    direction : np array
+    """
+
+    if convention == 'cartesian':
+        direction = np.mod(np.arctan2(u,v)*180/np.pi,360);
+    elif convention == 'nautical':
+        direction = np.mod(np.arctan2(-u,-v)*180/np.pi,360)
+    else:
+        print('please provide a valid convention: nautical or cartesian')
+
+    return direction