org.apache.commons.math.distribution

## Class WeibullDistributionImpl

• ### Field Summary

Fields
Modifier and Type Field and Description
`static double` `DEFAULT_INVERSE_ABSOLUTE_ACCURACY`
Default inverse cumulative probability accuracy
• ### Constructor Summary

Constructors
Constructor and Description
```WeibullDistributionImpl(double alpha, double beta)```
Creates weibull distribution with the given shape and scale and a location equal to zero.
```WeibullDistributionImpl(double alpha, double beta, double inverseCumAccuracy)```
Creates weibull distribution with the given shape, scale and inverse cumulative probability accuracy and a location equal to zero.
• ### Method Summary

All Methods
Modifier and Type Method and Description
`double` `cumulativeProbability(double x)`
For this distribution, X, this method returns P(X < `x`).
`double` `density(double x)`
Returns the probability density for a particular point.
`double` `getNumericalMean()`
Returns the mean of the distribution.
`double` `getNumericalVariance()`
Returns the variance of the distribution.
`double` `getScale()`
Access the scale parameter.
`double` `getShape()`
Access the shape parameter.
`double` `getSupportLowerBound()`
Returns the lower bound of the support for the distribution.
`double` `getSupportUpperBound()`
Returns the upper bound of the support for the distribution.
`double` `inverseCumulativeProbability(double p)`
For this distribution, X, this method returns the critical point x, such that P(X < x) = `p`.
`void` `setScale(double beta)`
Deprecated.
as of 2.1 (class will become immutable in 3.0)
`void` `setShape(double alpha)`
Deprecated.
as of 2.1 (class will become immutable in 3.0)
• ### Methods inherited from class org.apache.commons.math.distribution.AbstractContinuousDistribution

`reseedRandomGenerator, sample, sample`
• ### Methods inherited from class org.apache.commons.math.distribution.AbstractDistribution

`cumulativeProbability`
• ### Methods inherited from class java.lang.Object

`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
• ### Methods inherited from interface org.apache.commons.math.distribution.Distribution

`cumulativeProbability`
• ### Field Detail

• #### DEFAULT_INVERSE_ABSOLUTE_ACCURACY

`public static final double DEFAULT_INVERSE_ABSOLUTE_ACCURACY`
Default inverse cumulative probability accuracy
Since:
2.1
Constant Field Values
• ### Constructor Detail

• #### WeibullDistributionImpl

```public WeibullDistributionImpl(double alpha,
double beta)```
Creates weibull distribution with the given shape and scale and a location equal to zero.
Parameters:
`alpha` - the shape parameter.
`beta` - the scale parameter.
• #### WeibullDistributionImpl

```public WeibullDistributionImpl(double alpha,
double beta,
double inverseCumAccuracy)```
Creates weibull distribution with the given shape, scale and inverse cumulative probability accuracy and a location equal to zero.
Parameters:
`alpha` - the shape parameter.
`beta` - the scale parameter.
`inverseCumAccuracy` - the maximum absolute error in inverse cumulative probability estimates (defaults to `DEFAULT_INVERSE_ABSOLUTE_ACCURACY`)
Since:
2.1
• ### Method Detail

• #### cumulativeProbability

`public double cumulativeProbability(double x)`
For this distribution, X, this method returns P(X < `x`).
Specified by:
`cumulativeProbability` in interface `Distribution`
Parameters:
`x` - the value at which the CDF is evaluated.
Returns:
CDF evaluated at `x`.
• #### getShape

`public double getShape()`
Access the shape parameter.
Specified by:
`getShape` in interface `WeibullDistribution`
Returns:
the shape parameter.
• #### getScale

`public double getScale()`
Access the scale parameter.
Specified by:
`getScale` in interface `WeibullDistribution`
Returns:
the scale parameter.
• #### density

`public double density(double x)`
Returns the probability density for a particular point.
Overrides:
`density` in class `AbstractContinuousDistribution`
Parameters:
`x` - The point at which the density should be computed.
Returns:
The pdf at point x.
Since:
2.1
• #### inverseCumulativeProbability

`public double inverseCumulativeProbability(double p)`
For this distribution, X, this method returns the critical point x, such that P(X < x) = `p`.

Returns `Double.NEGATIVE_INFINITY` for p=0 and `Double.POSITIVE_INFINITY` for p=1.

Specified by:
`inverseCumulativeProbability` in interface `ContinuousDistribution`
Overrides:
`inverseCumulativeProbability` in class `AbstractContinuousDistribution`
Parameters:
`p` - the desired probability
Returns:
x, such that P(X < x) = `p`
Throws:
`java.lang.IllegalArgumentException` - if `p` is not a valid probability.
• #### setShape

```@Deprecated
public void setShape(double alpha)```
Deprecated. as of 2.1 (class will become immutable in 3.0)
Modify the shape parameter.
Specified by:
`setShape` in interface `WeibullDistribution`
Parameters:
`alpha` - the new shape parameter value.
• #### setScale

```@Deprecated
public void setScale(double beta)```
Deprecated. as of 2.1 (class will become immutable in 3.0)
Modify the scale parameter.
Specified by:
`setScale` in interface `WeibullDistribution`
Parameters:
`beta` - the new scale parameter value.
• #### getSupportLowerBound

`public double getSupportLowerBound()`
Returns the lower bound of the support for the distribution. The lower bound of the support is always 0 no matter the parameters.
Returns:
lower bound of the support (always 0)
Since:
2.2
• #### getSupportUpperBound

`public double getSupportUpperBound()`
Returns the upper bound of the support for the distribution. The upper bound of the support is always positive infinity no matter the parameters.
Returns:
upper bound of the support (always Double.POSITIVE_INFINITY)
Since:
2.2
• #### getNumericalMean

`public double getNumericalMean()`
Returns the mean of the distribution.
Returns:
the mean or Double.NaN if it's not defined
Since:
2.2
• #### getNumericalVariance

`public double getNumericalVariance()`
Returns the variance of the distribution.
Returns:
the variance (possibly Double.POSITIVE_INFINITY as for certain cases in `TDistributionImpl`) or Double.NaN if it's not defined
Since:
2.2