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author | Guido van Rossum <guido@python.org> | 1997-04-03 22:41:49 (GMT) |
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committer | Guido van Rossum <guido@python.org> | 1997-04-03 22:41:49 (GMT) |
commit | 571391b963058d5071a5372a4e55cb20c5476622 (patch) | |
tree | 263330f7ec90621008ae3a6426e284d1dd73805b /Doc/librandom.tex | |
parent | 6191551ad6b122d49878843cb2aab8070f10c180 (diff) | |
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New stuff by AMK.
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diff --git a/Doc/librandom.tex b/Doc/librandom.tex new file mode 100644 index 0000000..3bc92ce --- /dev/null +++ b/Doc/librandom.tex @@ -0,0 +1,71 @@ +\section{Standard Module \sectcode{random}} +\stmodindex{random} + +This module implements pseudo-random number generators for various +distributions: on the real line, there are functions to compute normal +or Gaussian, lognormal, negative exponential, gamma, and beta +distributions. For generating distribution of angles, the circular +uniform and von Mises distributions are available. + +The module exports the following functions, which are exactly +equivalent to those in the \code{whrandom} module: \code{choice}, +\code{randint}, \code{random}, \code{uniform}. See the documentation +for the \code{whrandom} module for these functions. + +The following functions specific to the \code{random} module are also +defined, and all return real values. Function parameters are named +after the corresponding variables in the distribution's equation, as +used in common mathematical practice; most of these equations can be +found in any statistics text. + +\renewcommand{\indexsubitem}{(in module random)} +\begin{funcdesc}{betavariate}{alpha\, beta} +Beta distribution. Conditions on the parameters are \code{alpha>-1} +and \code{beta>-1}. +Returned values will range between 0 and 1. +\end{funcdesc} + +\begin{funcdesc}{cunifvariate}{mean\, arc} +Circular uniform distribution. \var{mean} is the mean angle, and +\var{arc} is the range of the distribution, centered around the mean +angle. Both values must be expressed in radians, and can range +between 0 and \code{pi}. Returned values will range between +\code{mean - arc/2} and \code{mean + arc/2}. +\end{funcdesc} + +\begin{funcdesc}{expovariate}{lambd} +Exponential distribution. \var{lambd} is 1.0 divided by the desired mean. +(The parameter would be called ``lambda'', but that's also a reserved +word in Python.) Returned values will range from 0 to positive infinity. +\end{funcdesc} + +\begin{funcdesc}{gamma}{alpha\, beta} +Gamma distribution. (\emph{Not} the gamma function!) +Conditions on the parameters are \code{alpha>-1} and \code{beta>0}. +\end{funcdesc} + +\begin{funcdesc}{gauss}{mu\, sigma} +Gaussian distribution. \var{mu} is the mean, and \var{sigma} is the +standard deviation. This is slightly faster than the +\code{normalvariate} function defined below. +\end{funcdesc} + +\begin{funcdesc}{lognormvariate}{mu\, sigma} +Log normal distribution. If you take the natural logarithm of this +distribution, you'll get a normal distribution with mean \var{mu} and +standard deviation \var{sigma} \var{mu} can have any value, and \var{sigma} +must be greater than zero. +\end{funcdesc} + +\begin{funcdesc}{normalvariate}{mu\, sigma} +Normal distribution. \var{mu} is the mean, and \var{sigma} is the +standard deviation. +\end{funcdesc} + +\begin{funcdesc}{vonmisesvariate}{mu\, kappa} +\var{mu} is the mean angle, expressed in radians between 0 and pi, +and \var{kappa} is the concentration parameter, which must be greater +then or equal to zero. If \var{kappa} is equal to zero, this +distribution reduces to a uniform random angle over the range 0 to +\code{2*pi}. +\end{funcdesc} |