This function evaluates the complementary error function.

Function Return Value

ERFC — Function value.   (Output)

Required Arguments

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

FORTRAN 90 Interface

Generic:                              ERFC (X)

Specific:                             The specific interface names are S_ERFC and D_ERFC.

FORTRAN 77 Interface

Single:                                ERFC (X)

Double:                              The double precision function name is DERFC.

Description

The complementary error function, erfc(x), is defined to be

The argument x must not be so large that the result underflows. Approximately, x should be less than

where s = AMACH(1) (see the Reference Material section of this manual) is the smallest representable positive floating-point number.

Figure 5- 2 Plot of erfc (x)

Comments

Informational error

Type           Code

2                   1          The function underflows because X is too large.

Example

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

 

      USE ERFC_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    NOUT

      REAL       VALUE, X

!                                 Compute

      X     = 1.0

      VALUE = ERFC(X)

!                                 Print the results

      CALL UMACH (2, NOUT)

      WRITE (NOUT,99999) X, VALUE

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

      END

Output

 

ERFC( 1.000) =  0.157

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