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DRANDHYPERGEOMETRIC / SRANDHYPERGEOMETRIC

Generates a vector of random variates from a Hypergeometric distribution with probability, f(X), defined by: f(X) = [s! * m! * (p - s)!] / [X! * (s - X)! * (m - X)! * (p - m - s + X)! * p!], if X = max(0,m+s-p),...,min(l,m), otherwise f(X) = 0. Here p is the size of the population, (NP), s is the size of the sample taken from the population, (NS) and m is the number of labeled, or specified, items in the population, (M).

(Note that SRANDHYPERGEOMETRIC is the single precision version of DRANDHYPERGEOMETRIC. The argument lists of both routines are identical except that any double precision arguments of DRANDHYPERGEOMETRIC are replaced in SRANDHYPERGEOMETRIC by single precision arguments - type REAL in FORTRAN or type float in C).

— SUBROUTINE: DRANDHYPERGEOMETRIC (N,NP,NS,M,STATE,X,INFO)
— Input: INTEGER N

On input: number of variates required.
Constraint: N>=0.

— Input: INTEGER NP

On input: size of population.
Constraint: NP>=0.

— Input: INTEGER NS

On input: size of sample being taken from population.
Constraint: 0<=NS <=NP.

— Input: INTEGER M

On input: number of specified items in the population.
Constraint: 0<=M <=NP.

— Input/Output: INTEGER STATE(*)

The STATE vector holds information on the state of the base generator being used and as such its minimum length varies. Prior to calling DRANDHYPERGEOMETRIC STATE must have been initialized. See Initialization of the Base Generators for information on initialization of the STATE variable.
On input: the current state of the base generator.
On output: the updated state of the base generator.

— Output: INTEGER X(N)

On output: vector of variates from the specified distribution.

— Output: INTEGER INFO

On output: INFO is an error indicator. On successful exit, INFO contains 0. If INFO = -i on exit, the i-th argument had an illegal value. 

     Example:
     

     
          C      Generate 100 values from the Hypergeometric distribution
                 INTEGER LSTATE,N
                 PARAMETER (LSTATE=16,N=100)
                 INTEGER I,INFO,SEED(1),STATE(LSTATE)
                 INTEGER NP,NS,M
                 INTEGER X(N)
          C      Set the seed
                 SEED(1) = 1234
          
          C      Read in the distributional parameters
                 READ(5,*) NP,NS,M
          
          C      Initialize the STATE vector
                 CALL DRANDINITIALIZE(1,1,SEED,1,STATE,LSTATE,INFO)
          C      Generate N variates from the Hypergeometric distribution
                 CALL DRANDHYPERGEOMETRIC(N,NP,NS,M,STATE,X,INFO)
          
          C      Print the results
                 WRITE(6,*) (X(I),I=1,N)