mirror of https://github.com/python/cpython
72 lines
2.9 KiB
TeX
72 lines
2.9 KiB
TeX
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\section{Standard Module \sectcode{random}}
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\stmodindex{random}
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This module implements pseudo-random number generators for various
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distributions: on the real line, there are functions to compute normal
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or Gaussian, lognormal, negative exponential, gamma, and beta
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distributions. For generating distribution of angles, the circular
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uniform and von Mises distributions are available.
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The module exports the following functions, which are exactly
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equivalent to those in the \code{whrandom} module: \code{choice},
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\code{randint}, \code{random}, \code{uniform}. See the documentation
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for the \code{whrandom} module for these functions.
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The following functions specific to the \code{random} module are also
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defined, and all return real values. Function parameters are named
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after the corresponding variables in the distribution's equation, as
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used in common mathematical practice; most of these equations can be
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found in any statistics text.
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\renewcommand{\indexsubitem}{(in module random)}
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\begin{funcdesc}{betavariate}{alpha\, beta}
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Beta distribution. Conditions on the parameters are \code{alpha>-1}
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and \code{beta>-1}.
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Returned values will range between 0 and 1.
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\end{funcdesc}
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\begin{funcdesc}{cunifvariate}{mean\, arc}
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Circular uniform distribution. \var{mean} is the mean angle, and
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\var{arc} is the range of the distribution, centered around the mean
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angle. Both values must be expressed in radians, and can range
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between 0 and \code{pi}. Returned values will range between
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\code{mean - arc/2} and \code{mean + arc/2}.
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\end{funcdesc}
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\begin{funcdesc}{expovariate}{lambd}
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Exponential distribution. \var{lambd} is 1.0 divided by the desired mean.
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(The parameter would be called ``lambda'', but that's also a reserved
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word in Python.) Returned values will range from 0 to positive infinity.
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\end{funcdesc}
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\begin{funcdesc}{gamma}{alpha\, beta}
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Gamma distribution. (\emph{Not} the gamma function!)
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Conditions on the parameters are \code{alpha>-1} and \code{beta>0}.
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\end{funcdesc}
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\begin{funcdesc}{gauss}{mu\, sigma}
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Gaussian distribution. \var{mu} is the mean, and \var{sigma} is the
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standard deviation. This is slightly faster than the
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\code{normalvariate} function defined below.
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\end{funcdesc}
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\begin{funcdesc}{lognormvariate}{mu\, sigma}
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Log normal distribution. If you take the natural logarithm of this
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distribution, you'll get a normal distribution with mean \var{mu} and
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standard deviation \var{sigma} \var{mu} can have any value, and \var{sigma}
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must be greater than zero.
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\end{funcdesc}
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\begin{funcdesc}{normalvariate}{mu\, sigma}
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Normal distribution. \var{mu} is the mean, and \var{sigma} is the
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standard deviation.
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\end{funcdesc}
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\begin{funcdesc}{vonmisesvariate}{mu\, kappa}
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\var{mu} is the mean angle, expressed in radians between 0 and pi,
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and \var{kappa} is the concentration parameter, which must be greater
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then or equal to zero. If \var{kappa} is equal to zero, this
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distribution reduces to a uniform random angle over the range 0 to
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\code{2*pi}.
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\end{funcdesc}
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