r23140 - /trunk/lib/mathematics.py -- May 09, 2014 - 18:57

Author: tlinnet
Date: Fri May  9 18:57:38 2014
New Revision: 23140

URL: http://svn.gna.org/viewcvs/relax?rev=23140&view=rev
Log:
Added mathematics functions to lib/mathematics.py to calculate percentile.

This is because percentile is only available in numpy 1.9.

task #7792: (https://gna.org/task/?7792) Make the dx.map write suggest chi 
surface values.

Modified:
    trunk/lib/mathematics.py

Modified: trunk/lib/mathematics.py
URL: 
http://svn.gna.org/viewcvs/relax/trunk/lib/mathematics.py?rev=23140&r1=23139&r2=23140&view=diff
==============================================================================
--- trunk/lib/mathematics.py    (original)
+++ trunk/lib/mathematics.py    Fri May  9 18:57:38 2014
@@ -23,7 +23,7 @@
 """Module for basic mathematical operations."""
 
 # Python module imports.
-from math import ceil, log10
+from math import ceil, floor, log10
 
 
 def order_of_magnitude(value):
@@ -56,3 +56,30 @@
     
     # Calculate and return the value.
     return 10**(order_of_magnitude(value))
+
+
+def percentile(N, percent, key=lambda x:x):
+    """
+    Find the percentile of a list of values.
+
+    @parameter N:           Array of values.
+    @type N:                numpy float array
+    @parameter percent:     Float value from 0.0 to 1.0.
+    @type percent:          float
+    @parameter key:         Optional key function to compute value from each 
element of N.
+    @type key:              lambda function
+
+    @return:                The percentile of the values
+    """
+
+    # Sort N.
+    N.sort() 
+
+    k = (len(N)-1) * percent
+    f = floor(k)
+    c = ceil(k)
+    if f == c:
+        return key(N[int(k)])
+    d0 = key(N[int(f)]) * (c-k)
+    d1 = key(N[int(c)]) * (k-f)
+    return d0+d1