The N_ELEMENTS function returns the number of elements contained in an expression or variable.

## Examples

### Example 1

This example finds the number of elements in an array:

; Create an integer array:

I = INTARR(4, 5, 3, 6)

; Find the number of elements in I and print the result:

PRINT, N_ELEMENTS(I)

### Example 2

A typical use of N_ELEMENTS is to check if an optional input is defined, and if not, set it to a default value:

IF (N_ELEMENTS(roo) EQ 0) THEN roo=rooDefault

The original value of roo may be altered by a called routine, passing a different value back to the caller. Unless you intend for the routine to behave in this manner, you should prevent it by differentiating N_ELEMENTS’ parameter from your routine’s variable:

IF (N_ELEMENTS(roo) EQ 0) THEN rooUse=rooDefault $

` ELSE rooUse=roo`

### Example 3

This example finds the number of elements in a list:

list = LIST('zero', 1, 2.0)

PRINT, N_ELEMENTS(list)

## Syntax

*Result* = N_ELEMENTS(*Expression*)

## Return Value

Returns the number of elements.

## Arguments

### Expression

The expression for which the number of elements is to be returned. The number of elements in an array is equal to the product of its dimensions. If *Expression* is an undefined variable, N_ELEMENTS returns zero.

**Note: **If *Expression* is an instance of an object class that overloads the IDL_Object::_overloadSize method, the value returned by that method will be used to determine the number of elements. See IDL_Object for details.

## Keywords

None.

## Version History

Original |
Introduced |

## See Also

## Notes

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