X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=resources%2Ftools%2Fpresentation%2Futils.py;h=8f5630083b0991965935fee974dc4cfe32fbd25f;hb=82094363f6077e1b28845719db3a6191c0c93a99;hp=3fdec857740e5a6f70c8f09810b70f695584b041;hpb=c7cd008e11e76e22b8cebf5397b2b149251cbb4c;p=csit.git

diff --git a/resources/tools/presentation/utils.py b/resources/tools/presentation/utils.py
index 3fdec85774..8f5630083b 100644
--- a/resources/tools/presentation/utils.py
+++ b/resources/tools/presentation/utils.py
@@ -16,6 +16,7 @@
 
 import multiprocessing
 import subprocess
+import math
 import numpy as np
 import logging
 import csv
@@ -24,8 +25,8 @@ import prettytable
 from os import walk, makedirs, environ
 from os.path import join, isdir
 from shutil import move, Error
-from math import sqrt
 from datetime import datetime
+from pandas import Series
 
 from errors import PresentationError
 from jumpavg.BitCountingClassifier import BitCountingClassifier
@@ -51,11 +52,7 @@ def stdev(items):
     :returns: Stdev.
     :rtype: float
     """
-
-    avg = mean(items)
-    variance = [(x - avg) ** 2 for x in items]
-    stddev = sqrt(mean(variance))
-    return stddev
+    return Series.std(Series(items))
 
 
 def relative_change(nr1, nr2):
@@ -72,6 +69,32 @@ def relative_change(nr1, nr2):
     return float(((nr2 - nr1) / nr1) * 100)
 
 
+def relative_change_stdev(mean1, mean2, std1, std2):
+    """Compute relative standard deviation of change of two values.
+
+    The "1" values are the base for comparison.
+    Results are returned as percentage (and percentual points for stdev).
+    Linearized theory is used, so results are wrong for relatively large stdev.
+
+    :param mean1: Mean of the first number.
+    :param mean2: Mean of the second number.
+    :param std1: Standard deviation estimate of the first number.
+    :param std2: Standard deviation estimate of the second number.
+    :type mean1: float
+    :type mean2: float
+    :type std1: float
+    :type std2: float
+    :returns: Relative change and its stdev.
+    :rtype: float
+    """
+    mean1, mean2 = float(mean1), float(mean2)
+    quotient = mean2 / mean1
+    first = std1 / mean1
+    second = std2 / mean2
+    std = quotient * math.sqrt(first * first + second * second)
+    return (quotient - 1) * 100, std * 100
+
+
 def get_files(path, extension=None, full_path=True):
     """Generates the list of files to process.