The ERF function returns the value of the error function:

For real input, the error function 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, the error function is computed as *Sign* ∞ IGAMMA(0.5,*Z*^{2}), where *Sign* is taken from the real part of *Z*.

## Examples

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

PRINT, ERF(0.4D)

IDL prints:

0.42839236

## Syntax

*Result* = ERF(*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 ERF function also accepts complex arguments.

## Arguments

### Z

The expression for which the 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

Pre 4.0 |
Introduced |

5.6 |
Z argument accepts complex input |