edu.northwestern.at.utils.math.distributions

## Class ErrorFunction

• java.lang.Object
• edu.northwestern.at.utils.math.distributions.ErrorFunction

• ```public class ErrorFunction
extends java.lang.Object```
Gaussian error function distribution functions.
• ### Constructor Summary

Constructors
Modifier Constructor and Description
`protected ` `ErrorFunction()`
Make class non-instantiable but inheritable.
• ### Method Summary

Methods
Modifier and Type Method and Description
`protected static double` ```calerf(double x, int jint)```
Calculate value of Gaussian error function.
`static double` `errorFunction(double x)`
Error function.
`static double` `errorFunctionComplement(double x)`
Error function complement.
`static double` `errorFunctionComplementInverseBad(double x)`
`static double` `errorFunctionInverse(double z)`
Inverse error function.
`static double` `errorFunctionInverseBad(double x)`
Percentage points of error function distribution.
• ### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
• ### Constructor Detail

• #### ErrorFunction

`protected ErrorFunction()`
Make class non-instantiable but inheritable.
• ### Method Detail

• #### calerf

```protected static double calerf(double x,
int jint)```
Calculate value of Gaussian error function.
Parameters:
`x` -
`jint` - Selects type of error function evaluation. = 0: error function = 1: complement of error function. = 2: exp(xx) * complement of error function.
Returns:
Error function value.

The program returns erfc=0 for x > XBIG (see below); erfcx = XINF for x < XNEG; and erfcx = 0 for x >= XMAX.

The main computation evaluates near-minimax approximations from "Rational Chebyshev approximations for the error function" by W. J. Cody, Math. Comp., 1969, PP. 631-638. This java code is a straightforward translation of W. J. Cody's Fortran CALERF function.

• #### errorFunction

`public static double errorFunction(double x)`
Error function.
Parameters:
`x` - Error function argument.
Returns:
Error function value.
• #### errorFunctionComplement

`public static double errorFunctionComplement(double x)`
Error function complement.
Parameters:
`x` - Error function argument.
Returns:
Error function complement value.
• #### errorFunctionInverse

`public static double errorFunctionInverse(double z)`
Inverse error function.
Parameters:
`z` - Probability for which matching percentage point of error function is desired.
Returns:
Error function percentage point.

The percentage point is computed using the relationship between the error function and the normal distribution.

`public static double errorFunctionInverseBad(double x)`
`x` - Parameter for which percentage point is desired.
`public static double errorFunctionComplementInverseBad(double x)`