This function evaluates the Weibull cumulative distribution function.
Function Return Value
WBLDF — Function value, the probability that a Weibull random variable takes a value less than or equal to X. (Output)
Required Arguments
X — Argument for which the Weibull cumulative distribution function is to be evaluated. (Input)
A — Scale parameter. (Input)
B — Shape parameter. (Input)
FORTRAN 90 Interface
Generic: WBLDF (X, A, B)
Specific: The specific interface names are S_WBLDF and D_WBLDF.
FORTRAN 77 Interface
Single: WBLDF (X, A, B)
Double: The double precision name is DWBLDF.
Description
The function WBLDF evaluates the Weibull cumulative distribution function with scale parameter A and shape parameter B, defined
To deal with potential loss of precision for small values
of 
, the difference expression
for p is re-written as
,
and the right factor is accurately evaluated using EXPRL.
Example
In this example, we evaluate the Weibull cumulative
distribution function at X =
1.5, A =
1.0,
B =
2.0.
USE
UMACH_INT
USE
WBLDF_INT
IMPLICIT NONE
INTEGER NOUT
REAL X, A, B, PR
CALL UMACH(2, NOUT)
X = 1.5
A = 1.0
B = 2.0
PR = WBLDF(X, A, B)
WRITE (NOUT, 99999) X, A, B, PR
99999 FORMAT (' WBLDF(', F4.2, ', ', F4.2, ', ', F4.2, ') = ', F6.4)
END
Output
WBLDF(1.50, 1.00, 2.00) = 0.8946
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