import math
import functools
def percentile(N, percent, key=lambda x:x):
"""
Find the percentile of a list of values.
@parameter N - is a list of values. Note N MUST BE already sorted.
@parameter percent - a float value from 0.0 to 1.0.
@parameter key - optional key function to compute value from each element of N.
@return - the percentile of the values
"""
if not N:
return None
k = (len(N)-1) * percent
f = math.floor(k)
c = math.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
# median is 50th percentile.
median = functools.partial(percentile, percent=0.5)
Diff to Previous Revision
--- revision 1 2007-04-17 08:47:01
+++ revision 2 2011-04-25 03:41:08
@@ -18,8 +18,8 @@
c = math.ceil(k)
if f == c:
return key(N[int(k)])
- d0 = key(N[int(f)]) * (k-f)
- d1 = key(N[int(c)]) * (c-k)
+ d0 = key(N[int(f)]) * (c-k)
+ d1 = key(N[int(c)]) * (k-f)
return d0+d1
# median is 50th percentile.
