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DRANDGEOMETRIC / SRANDGEOMETRIC

Generates a vector of random variates from a Geometric distribution with probability, f(X), defined by: f(X) = P * (1 - P)^(X-1), X=1,2,....

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

— SUBROUTINE: DRANDGEOMETRIC (N,P,STATE,X,INFO)
— Input: INTEGER N

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

— Input: DOUBLE PRECISION P

On input: distribution parameter.
Constraint: 0<=P <1.

— 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 DRANDGEOMETRIC 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 Geometric distribution
                 INTEGER LSTATE,N
                 PARAMETER (LSTATE=16,N=100)
                 INTEGER I,INFO,SEED(1),STATE(LSTATE)
                 DOUBLE PRECISION P
                 INTEGER X(N)
          C      Set the seed
                 SEED(1) = 1234
          
          C      Read in the distributional parameters
                 READ(5,*) P
          
          C      Initialize the STATE vector
                 CALL DRANDINITIALIZE(1,1,SEED,1,STATE,LSTATE,INFO)
          C      Generate N variates from the Geometric distribution
                 CALL DRANDGEOMETRIC(N,P,STATE,X,INFO)
          
          C      Print the results
                 WRITE(6,*) (X(I),I=1,N)