Welcome to the Harris Geospatial product documentation center. Here you will find reference guides, help documents, and product libraries.


ERF

ERF

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,Z2), 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

See Also


ERFC, ERFCX, EXPINT, GAMMA, IGAMMA



© 2017 Exelis Visual Information Solutions, Inc. |  Legal
My Account    |    Buy    |    Contact Us