IDAX.PWEIBULL - Cumulative Weibull distribution

The PWEIBULL function returns the probability that the value of a variable that follows the Weibull distribution is smaller or equal to x.

Syntax

IDAX.PWEIBULL(DOUBLE x, DOUBLE scale, DOUBLE
kShape)

Parameter descriptions

x
Mandatory.
The value that is to be computed.
Min: 0
Data type: DOUBLE
scale
Mandatory.
The scale of the distribution.
Min: 0.00000000001
Data type: DOUBLE
kShape
Mandatory.
The shape of the distribution.
The following conditions apply to the kShape parameter:
  • If the value of the shape parameter is <1, the failure rate decreases over time.
  • If the value of the shape parameter is 1, the failure rate is constant over time.
  • If the value of the shape parameter is >1, the failure rate increases over time.
Min: 0.00000000001
Data type: DOUBLE

The cumulative Weibull distribution has the closed form PWEIBULL(x,scale,kShape)=1-exp(- (x/scale)^kShape) for all positive x values, positive scale values, and positive kShape values.

The Exponential distribution is a special case of the Weibull distribution: PWEIBULL(x,scale,1)=PEXP(x,scale).

If x is less than 0, or if scale or shape are 0 or less, PWEIBULL(x,scale,kShape) is null.

Returned information

DOUBLE the probability density at point x.