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C Library Functions  - chsran (3)

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NAME

chsran(3f) - [M_datapac:RANDOM] generate chi-square random numbers

CONTENTS

Synopsis
Description
Input Arguments
Output Arguments
Examples
Author
Maintainer
License
References

SYNOPSIS

SUBROUTINE CHSRAN(N,Nu,Iseed,X)

       INTEGER,intent(in)        :: N
       INTEGER,intent(in)        :: Nu
       INTEGER,intent(inout)     :: Iseed
       REAL(kind=wp),intent(out) :: X(:)

DESCRIPTION

CHSRAN(3f) generates a random sample of size n from the chi-squared distribution with integer degrees of freedom parameter = NU.

INPUT ARGUMENTS

N	The desired integer number of random numbers to be generated.
NU	The integer degrees of freedom (parameter) for the chi-squared distribution. NU should be a positive integer variable.
ISEED	An integer seed value. Should be set to a non-negative value to start a new sequence of values. Will be set to -1 on return to indicate the next call should continue the current random sequence walk.

OUTPUT ARGUMENTS

--X	A vector (of dimension at least N) into which the generated random sample of size N from the chi-squared distribution will be placed.

EXAMPLES

Sample program:

   program demo_chsran
   use m_datapac, only : chsran, plott, label, plotxt, sort
   implicit none
   integer,parameter :: n=4000
   integer           :: iseed
   integer           :: Nu
   real              :: x(n)
      call label(’chsran’)
      Nu=8
      iseed=12345
      call chsran(N,Nu,Iseed,X)
      call plotxt(x,n)
      call sort(x,n,x) ! sort to show distribution
      call plotxt(x,n)
   end program demo_chsran

Results:

    THE FOLLOWING IS A PLOT OF X(I) (VERTICALLY) VERSUS I (HORIZONTALLY
                      I-----------I-----------I-----------I-----------I
     0.3098298E+02 -                                                  X
     0.2972390E+02 I
     0.2846483E+02 I
     0.2720575E+02 I         X
     0.2594668E+02 I        X                 X
     0.2468760E+02 I
     0.2342853E+02 -      X  X                                     X
     0.2216945E+02 I   X             X  X          X              X  X
     0.2091037E+02 I     X     X  X   X X     XX   X  X  XX       X
     0.1965130E+02 I    XXX XX X  XX  X XXX  X     XX  X   XX    X
     0.1839222E+02 I    XXX  X X  XXXXXXX XXX XXX XXXX XX X   X   X XXX
     0.1713315E+02 I   XX X XXX XX XXXX XXXXX XXXX XXX  XXXXX  XXX XX
     0.1587407E+02 -  XXXXXX XXXXXX XX XXXX XX XXX  X  XX XXXX XX XXXX
     0.1461500E+02 I   XXXXXXXXX XX XXXXXXXXX XX XXX XXXXXX X XXXXXXXX
     0.1335592E+02 I  X XXXXX XXXXXXX XXX XXX XX XXXXXXX XXXXXXXX XXXX
     0.1209685E+02 I  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.1083777E+02 I  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.9578695E+01 I  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.8319620E+01 -   XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.7060543E+01 I  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.5801468E+01 I  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.4542393E+01 I  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.3283318E+01 I  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.2024242E+01 I  XXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     0.7651675E+00 -   X X X        X      XX  X   XXX X XX    X
                      I-----------I-----------I-----------I-----------I
               0.1000E+01  0.1001E+04  0.2000E+04  0.3000E+04  0.4000E+04

    THE FOLLOWING IS A PLOT OF X(I) (VERTICALLY) VERSUS I (HORIZONTALLY
                      I-----------I-----------I-----------I-----------I
     0.3098298E+02 -                                                  X
     0.2972390E+02 I
     0.2846483E+02 I
     0.2720575E+02 I                                                  X
     0.2594668E+02 I                                                  X
     0.2468760E+02 I
     0.2342853E+02 -                                                  X
     0.2216945E+02 I                                                  X
     0.2091037E+02 I                                                  X
     0.1965130E+02 I                                                 XX
     0.1839222E+02 I                                                 X
     0.1713315E+02 I                                                XX
     0.1587407E+02 -                                               XX
     0.1461500E+02 I                                              XX
     0.1335592E+02 I                                            XXX
     0.1209685E+02 I                                         XXXX
     0.1083777E+02 I                                      XXXX
     0.9578695E+01 I                                 XXXXXX
     0.8319620E+01 -                            XXXXXX
     0.7060543E+01 I                     XXXXXXXX
     0.5801468E+01 I               XXXXXXX
     0.4542393E+01 I         XXXXXXX
     0.3283318E+01 I    XXXXXX
     0.2024242E+01 I  XXX
     0.7651675E+00 -  X
                      I-----------I-----------I-----------I-----------I
               0.1000E+01  0.1001E+04  0.2000E+04  0.3000E+04  0.4000E+04

AUTHOR

The original DATAPAC library was written by James Filliben of the Statistical Engineering Division, National Institute of Standards and Technology.

MAINTAINER

John Urban, 2022.05.31

LICENSE

CC0-1.0

REFERENCES

o	Tocher, The Art of Simulation, 1963, pages 34-35.
o	Mood and Grable, Introduction to the Theory of Statistics, 1963, pages 226-227.
o	Johnson and Kotz, Continuous Univariate Distributions--1, 1970, page 171.
o	Hastings and Peacock, Statistical Distributions--A Handbook for Students and Practitioners, 1975, page 48.

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Nemo Release 3.1

chsran (3)

February 23, 2025

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