Package org.apache.commons.math.special

Class Erf

  • public class Erf
extends java.lang.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) $

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      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

    • 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)