[ 
https://issues.apache.org/jira/browse/STATISTICS-31?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Benjamin W Trent updated STATISTICS-31:
---------------------------------------
    Description: 
It is useful to know the [survival 
function|[https://en.wikipedia.org/wiki/Survival_function]] of a number given a 
continuous distribution.

While this can be approximated with
{noformat}
1 - cdf(x){noformat}
, there is an opportunity for greater accuracy in certain distributions.

 

A good example of this is the gamma distribution. The survival function for 
that distribution would probably look similar to:

 

```java

@Override
 public double survivalProbability(double x) {
     if (x <= SUPPORT_LO)

{         return 1;     }

else if (x >= SUPPORT_HI)

{         return 0;     }

    return RegularizedGamma.Q.value(shape, x / scale);
 }

```

 

  was:
It is useful to know the [survival 
function|[https://en.wikipedia.org/wiki/Survival_function]] of a number given a 
continuous distribution.

While this can be approximated with `1 - cdf(x)`, there is an opportunity for 
greater accuracy in certain distributions.

A good example of this is the gamma distribution. The survival function for 
that distribution would probably look similar to:

 

```java

@Override
public double survivalProbability(double x) {
    if (x <= SUPPORT_LO) {
        return 1;
    } else if (x >= SUPPORT_HI) {
        return 0;
    }
    return RegularizedGamma.Q.value(shape, x / scale);
}

```

 


> Add survival probability function to continuous distributions
> -------------------------------------------------------------
>
>                 Key: STATISTICS-31
>                 URL: https://issues.apache.org/jira/browse/STATISTICS-31
>             Project: Apache Commons Statistics
>          Issue Type: New Feature
>            Reporter: Benjamin W Trent
>            Priority: Major
>
> It is useful to know the [survival 
> function|[https://en.wikipedia.org/wiki/Survival_function]] of a number given 
> a continuous distribution.
> While this can be approximated with
> {noformat}
> 1 - cdf(x){noformat}
> , there is an opportunity for greater accuracy in certain distributions.
>  
> A good example of this is the gamma distribution. The survival function for 
> that distribution would probably look similar to:
>  
> ```java
> @Override
>  public double survivalProbability(double x) {
>      if (x <= SUPPORT_LO)
> {         return 1;     }
> else if (x >= SUPPORT_HI)
> {         return 0;     }
>     return RegularizedGamma.Q.value(shape, x / scale);
>  }
> ```
>  



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