BETPR
This function evaluates the beta probability density function.
Function Return Value
BETPR — Function value, the value of the probability density function. (Output)
Required Arguments
X — Argument for which the beta probability density function is to be evaluated. (Input)
PIN — First beta distribution parameter. (Input)
PIN must be positive.
QIN — Second beta distribution parameter. (Input)
QIN must be positive.
FORTRAN 90 Interface
Generic: BETPR (X, PIN, QIN)
Specific: The specific interface names are S_BETPR and D_BETPR.
FORTRAN 77 Interface
Single: BETPR (X, PIN, QIN)
Double: The double precision name is DBETPR.
Description
The function BETPR evaluates the beta probability density function with parameters PIN and QIN. Using x = X, a = PIN and b = QIN, the beta distribution is defined as
where beta function B(a, b) is computed using IMSL function BETA (see the Special Functions book, Chapter 4, Gamma and Related Functions).
Example
In this example, we evaluate the probability function at X = 0.75, PIN = 2.0, QIN = 0.5.
USE UMACH_INT
USE BETPR_INT
IMPLICIT NONE
INTEGER NOUT
REAL X, PIN, QIN, PR
CALL UMACH(2, NOUT)
X = .75
PIN = 2.0
QIN = 0.5
PR = BETPR(X, PIN, QIN)
WRITE (NOUT, 99999) X, PIN, QIN, PR
99999 FORMAT (' BETPR(', F4.2, ', ', F4.2, ', ', F4.2, ') = ', F6.4)
END
Output
BETPR(0.75, 2.00, 0.50) = 1.1250
