This function evaluates the error function.

Function Return Value

ERF — Function value.   (Output)

Required Arguments

X — Argument for which the function value is desired.   (Input)

FORTRAN 90 Interface

Generic:                              ERF (X)

Specific:                             The specific interface names are S_ERF and D_ERF.

FORTRAN 77 Interface

Single:                                ERF (X)

Double:                              The double precision function name is DERF.

Description

The error function, erf(x), is defined to be

All values of x are legal.

Figure 5- 1 Plot of erf (x)

Example

In this example, erf(1.0) is computed and printed.

 

      USE ERF_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    NOUT

      REAL       VALUE, X

!                                 Compute

      X     = 1.0

      VALUE = ERF(X)

!                                 Print the results

      CALL UMACH (2, NOUT)

      WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' ERF(', F6.3, ') = ', F6.3)

      END

Output

 

ERF( 1.000) =  0.843

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