EXPDF

This function evaluates the exponential cumulative distribution function.

Function Return Value

EXPDF — Function value, the probability that an exponential random variable takes a value less than or equal to X. (Output)

Required Arguments

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

B — Scale parameter of the exponential distribution function. (Input)

FORTRAN 90 Interface

Generic: EXPDF (X, B)

Specific: The specific interface names are S_EXPDF and D_EXPDF.

FORTRAN 77 Interface

Single: EXPDF (X, B)

Double: The double precision name is DEXPDF.

Description

The function EXPDF evaluates the exponential cumulative distribution function (CDF), defined:

 

where

 

is the exponential probability density function (PDF).

Example

In this example, we evaluate the probability function at X = 2.0, B = 1.0.

 

USE UMACH_INT

USE EXPDF_INT

IMPLICIT NONE

INTEGER NOUT

REAL X, B, PR

CALL UMACH(2, NOUT)

X = 2.0

B = 1.0

PR = EXPDF(X, B)

WRITE (NOUT, 99999) X, B, PR

99999 FORMAT (' EXPDF(', F4.2, ', ', F4.2, ') = ', F6.4)

END

Output

 

EXPDF(2.00, 1.00) = 0.8647