This function evaluates the discrete geometric cumulative probability distribution function.

Function Return Value

GEODF — Function value, the probability that a geometric random variable takes a value less than or equal to IX.   (Output)

Required Arguments

IX — Argument for which the geometric cumulative distribution function is to be evaluated.   (Input)

PIN — Probability parameter for each independent trial (the probability of success for each independent trial).   PIN must be in the open interval (0, 1).  (Input)

FORTRAN 90 Interface

Generic:                              GEODF (IX, PIN)

Specific:                             The specific interface names are S_GEODF and D_GEODF.

FORTRAN 77 Interface

Single:                                GEODF (IX, PIN)

Double:                              The double precision name is DGEODF.

Description

The function GEODF evaluates the discrete geometric cumulative probability distribution function with parameter p = PIN, defined

  .

The return value is the probability that up to x trials would be observed before observing a success.

Example

In this example, we evaluate the probability function at IX = 3, PIN = 0.25.

 

      USE UMACH_INT
      USE GEODF_INT
      IMPLICIT NONE

      INTEGER NOUT, IX

      REAL PIN, PR

      CALL UMACH(2, NOUT)

     

      IX = 3

      PIN = 0.25e0

      PR = GEODF(IX, PIN)

      WRITE (NOUT, 99999) IX, PIN, PR

99999 FORMAT (' GEODF(', I2, ', ', F4.2, ') = ', F10.6)

      END

Output

 

GEODF( 3, 0.25) =   0.683594 

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