r11434 - /1.3/maths_fns/order_parameters.py -- August 07, 2010 - 21:31

Author: bugman
Date: Sat Aug  7 21:31:05 2010
New Revision: 11434

URL: http://svn.gna.org/viewcvs/relax?rev=11434&view=rev
Log:
Created maths_fns.order_parameters.iso_cone_theta_to_S() function for angle 
to order param conversion.


Modified:
    1.3/maths_fns/order_parameters.py

Modified: 1.3/maths_fns/order_parameters.py
URL: 
http://svn.gna.org/viewcvs/relax/1.3/maths_fns/order_parameters.py?rev=11434&r1=11433&r2=11434&view=diff
==============================================================================
--- 1.3/maths_fns/order_parameters.py (original)
+++ 1.3/maths_fns/order_parameters.py Sat Aug  7 21:31:05 2010
@@ -23,6 +23,29 @@
 # Module docstring.
 """Module for the conversion of order parameters to specific model 
parameters and vice versa."""
 
+# Python module imports.
+from math import cos
+
+
+def iso_cone_theta_to_S(theta):
+    """Convert the isotropic cone angle to the order parameter S.
+
+    This uses Woessner's diffusion in a cone order parameter defined as::
+
+        S = 1/2 (1 + cos(theta)) * cos(theta)
+
+    @param theta:   The isotropic cone angle.
+    @type theta:    float
+    @return:        The order parameter value.
+    @rtype:         float
+    """
+
+    # Convert.
+    S = 0.5 * (1.0 + cos(theta)) * cos(theta)
+
+    # Return the order parameter.
+    return S
+
 
 def iso_cone_S_to_cos_theta(S):
     """Convert the isotropic cone order parameter S into the cosine of the 
cone angle.