Routines (alphabetical) > Routines: E > ERFCX

# ERFCX

The ERFCX function returns the value of the scaled complementary error function:

For real input, ERFCX is computed using rational functions, as described in “Rational Chebyshev approximations for the error function,” W. J. Cody, Math. Comp., 1969, pp. 631-638. For complex input, ERFCX is computed as EXP(Z2)ERFC(Z).

## Examples

To find the scaled complementary error function of 0.4 and print the result, enter:

PRINT, ERFCX(0.4D)

IDL prints:

0.67078779

## Syntax

Result = ERFCX(Z)

## Return Value

The result is double-precision if the argument is double-precision, otherwise the result is floating-point. The result always has the same structure as Z. The ERFCX function also accepts complex arguments.

## Arguments

### Z

The expression for which the scaled complementary error function is to be evaluated. Z may be complex.

## Keywords

### Thread Pool Keywords

This routine is written to make use of IDL’s thread pool, which can increase execution speed on systems with multiple CPUs. The values stored in the !CPU system variable control whether IDL uses the thread pool for a given computation. In addition, you can use the thread pool keywords TPOOL_MAX_ELTS, TPOOL_MIN_ELTS, and TPOOL_NOTHREAD to override the defaults established by !CPU for a single invocation of this routine. See Thread Pool Keywords.

## Version History

5.5 | Introduced
5.6 | Z argument accepts complex input

## See Also

ERF, ERFC