The FINITE function identifies whether or not a given argument is finite.

## Examples

### Example 1

To find out if the logarithm of 5.0 is finite, enter:

PRINT, FINITE(ALOG(5.0))

IDL prints “1” because the argument is finite.

See Additional Examples for more examples of using FINITE.

## Syntax

*Result* = FINITE( *X* [, /INFINITY] [, /NAN] [, SIGN=*value*])

## Return Value

Returns 1 (True) if its argument is finite. If the argument is infinite or not a defined number (*NaN*), the FINITE function returns 0 (False). The result is a byte expression of the same structure as the argument *X*.

## Arguments

### X

A floating-point, double-precision, or complex scalar or array expression. Strings are first converted to floating-point. This function returns 1 (True) for byte, integer, or longword arguments.

## Keywords

### INFINITY

Set this keyword to cause FINITE to return True if the *X* argument is the IEEE special floating-point value *Infinity* (either positive or negative), or False otherwise.

### NAN

Set this keyword to cause FINITE to return True if the *X* argument is the IEEE special floating-point value “Not A Number” (*NaN*), or False otherwise.

### SIGN

If the INFINITY or NAN keyword is set, then set this keyword to one of the following values:

Value |
Description |

> 0 |
If the INFINITY keyword is set, return True (1) if |

0 (the default) |
The sign of |

< 0 |
If the INFINITY is set, return True (1) if |

If neither the INFINITY nor NAN keyword is set, then this keyword is ignored.

### 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 for details.

## Additional Examples

### Example 2

To determine which elements of an array are infinity or NaN (Not a Number) values:

A = FLTARR(10)

; Set some values to +/-NaN and positive or negative Infinity:

A[3] = !VALUES.F_NAN

A[4] = -!VALUES.F_NAN

A[6] = !VALUES.F_INFINITY

A[7] = -!VALUES.F_INFINITY

Find the location of values in A that are positive or negative Infinity:

PRINT, WHERE(FINITE(A, /INFINITY))

IDL prints:

6 7

Find the location of values in A that are NaN:

PRINT, WHERE(FINITE(A, /NAN))

IDL prints:

3 4

Find the location of values in A that are negative Infinity:

PRINT, WHERE(FINITE(A, /INFINITY, SIGN=-1))

IDL prints:

` 7`

Find the location of values in A that are +NaN:

PRINT, WHERE(FINITE(A, /NAN, SIGN=1))

IDL prints:

` 3`

**Note: **On some platforms, there is no distinction between +NaN and -NaN.

## Version History

Original |
Introduced |

a = [1,-!values.f_infinity,3,4,!values.f_nan,6,7,8,!values.f_infinity,10,11,-!values.f_nan]

print,where(~finite(a)) IDL prints:

1 4 8 11