scipy tutorial - Baustatik-Info-Server

SciPy Reference Guide, Release 0.8.dev
Note how, by virtue of how matrix analytic functions are defined, the Bessel function has acted on the matrix eigenvalues.
1.9 Statistics
1.9.1 Introduction
SciPy has a tremendous number of basic statistics routines with more easily added by the end user (if you create
one please contribute it). All of the statistics functions are located in the sub-package scipy.stats and a fairly
complete listing of these functions can be had using info(stats).
Random Variables
There are two general distribution classes that have been implemented for encapsulating continuous random variables
and discrete random variables . Over 80 continuous random variables and 10 discrete random variables have been
implemented using these classes. The list of the random variables available is in the docstring for the stats subpackage.
Note: The following is work in progress
1.9.2 Distributions
First some imports
>>> import numpy as np
>>> from scipy import stats
>>> import warnings
>>> warnings.simplefilter(’ignore’, DeprecationWarning)
We can obtain the list of available distribution through introspection:
>>> dist_continu = [d for d in dir(stats) if
... isinstance(getattr(stats,d), stats.rv_continuous)]
>>> dist_discrete = [d for d in dir(stats) if
... isinstance(getattr(stats,d), stats.rv_discrete)]
>>> print ’number of continuous distributions:’, len(dist_continu)
number of continuous distributions: 84
>>> print ’number of discrete distributions: ’, len(dist_discrete)
number of discrete distributions: 12
Distributions can be used in one of two ways, either by passing all distribution parameters to each method call or by
freezing the parameters for the instance of the distribution. As an example, we can get the median of the distribution
by using the percent point function, ppf, which is the inverse of the cdf:
>>> print stats.nct.ppf(0.5, 10, 2.5)
2.56880722561
>>> my_nct = stats.nct(10, 2.5)
>>> print my_nct.ppf(0.5)
2.56880722561
help(stats.nct) prints the complete docstring of the distribution. Instead we can print just some basic information:
1.9. Statistics 49