Source code for expyriment.misc.statistics

"""
The statistics module.

This module contains miscellaneous stastistical functions for expyriment.

"""

__author__ = 'Florian Krause <florian@expyriment.org>, \
Oliver Lindemann <oliver@expyriment.org>'
__version__ = '0.6.3+'
__revision__ = '0a47722d7fb0'
__date__ = 'Fri Jul 26 11:31:53 2013 +0200'


[docs]def sum(data): """Returns the sum of data. The function ignores all non-numerical elements in the data and returns None if no numerical element has been found. In contrast to standard math and numpy functions, this function is robust against type violations. Parameters ---------- data : list list of numerical data Returns ------- out : float or None """ s = 0 elem_found = False for v in data: try: s += v elem_found = True except: pass if elem_found: return s else: return None
[docs]def mode(data): """Returns the mode, that is, the most frequent value in data. Parameters ---------- data : list list of numerical data Returns ------- out : float or None """ freq = frequence_table(data) Fmax = max(freq.values()) for x, f in freq.items(): if f == Fmax: break return x
[docs]def mean(data): """Returns the mean of data. Notes ----- The function ignores all non-numerical elements in the data and returns None if no numerical element has been found. In contrast to standard math and numpy functions, this function is robust against type violations. Parameters ---------- data : list list of numerical data Returns ------- out : float or None """ s = 0 cnt = 0 for v in data: try: s += v cnt += 1 except: pass if cnt == 0: return None else: return float(s) / float(cnt)
[docs]def median(data): """Returns the median of data. Notes ----- The function ignores all non-numerical elements in the data and returns None if no numerical element has been found. In contrast to standard math and numpy functions, this function is robust against type violations. Parameters ---------- data : list list of numerical data Returns ------- out : float or None """ tmp = [] for elem in data: # remove non numerics if isinstance(elem, (int, long, float)): tmp.append(elem) data = sorted(tmp) if len(data) % 2 == 1: return data[(len(data) - 1) / 2 ] else: lower = data[len(data) / 2 - 1] upper = data[len(data) / 2] return (float(lower + upper)) / 2.0
[docs]def frequence_table(data): """Returns the frequency table of the data as dictionary. Parameters ---------- data : list list of numerical data Returns ------- out : dict `dict.keys` : values, `dict.values` : frequencies """ freq = {} for x in data: freq[x] = freq.get(x, 0) + 1 return freq