## org.apache.commons.math.special
Class Erf

    java.lang.Object
      org.apache.commons.math.special.Erf

    public class Erf

extends Object

This is a utility class that provides computation methods related to the error functions.

Version:
  $Revision: 1054186 $ $Date: 2011-01-01 03:28:46 +0100 (sam. 01 janv. 2011) $

Constructor Summary
`private` `Erf()` Default constructor.

Method Summary
`static double` `erf(double x)` Returns the error function
`static double` `erfc(double x)` Returns the complementary error function

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### Erf

    private Erf()

  Default constructor. Prohibit instantiation.

Method Detail

### erf

    public static double erf(double x)
                      throws MathException

  Returns the error function

  erf(x) = 2/√π 0∫x e-t2dt

  This implementation computes erf(x) using the `regularized gamma function`, following Erf, equation (3)

  The value returned is always between -1 and 1 (inclusive). If `abs(x) > 40`, then `erf(x)` is indistinguishable from either 1 or -1 as a double, so the appropriate extreme value is returned.

  Parameters:
    `x` - the value.
  Returns:
    the error function erf(x)
  Throws:
    `MathException` - if the algorithm fails to converge.
  See Also:
    `Gamma.regularizedGammaP(double, double, double, int)`

### erfc

    public static double erfc(double x)
                       throws MathException

  Returns the complementary error function

  erfc(x) = 2/√π x∫∞ e-t2dt
  = 1 - `erf(x)`

  This implementation computes erfc(x) using the `regularized gamma function`, following Erf, equation (3).

  The value returned is always between 0 and 2 (inclusive). If `abs(x) > 40`, then `erf(x)` is indistinguishable from either 0 or 2 as a double, so the appropriate extreme value is returned.

  Parameters:
    `x` - the value
  Returns:
    the complementary error function erfc(x)
  Throws:
    `MathException` - if the algorithm fails to converge
  Since:
    2.2
  See Also:
    `Gamma.regularizedGammaQ(double, double, double, int)`

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