# Size

## Size(A)

Size returns the total number of elements in array «A».

When applied to a scalar (a zero-dimensional array), it returns 1.

Size does not count elements that are contained within a reference. So if a reference occurs in a cell of an array, it will be counted as one, even if it points to an array that contains many cells.

## Library

Array library

## Length of an index

To get the length of an index, use IndexLength(I). (introduced in Analytica 5.0).

When used on an index, `Size(I)`

usually, but not always, returns the length of the index. However, because Size actually returns the size of the *value* of its parameter, this does not give the index length when the parameter is a self-indexed array, or when the parameter is the dynamic index in a dynamic loop (usually the Time index).

When the identifier is the local identifier that has been declared as an index, then `Size(I)`

does return the index length rather than the value length, even when `I`

is a self-indexed array or dynamic index.

Two other reliable ways to obtain the length of an index are:

`Size(IndexValue(I))`

or

`Sum(1, I)`

Or by using a User-Defined Function:

`Function Index_Length(I : Index) := Size(I)`

.

## Length of the implicit dimension

All dimensions of an Analytica array correspond to an explicit index object, except for one -- the implicit dimension. See the article Implicit Dimensions for more details.

When «A» has an implicit dimension, its length can be obtained using:

`Size(A, listLen: true)`

You can also use this to determine the number of repeated parameters supplied to a User-Defined Function. For example:

`Function GeoAve(x : ... Number )`

`Definition: Exp(Sum(Ln(x))/Size(x, ListLen: true))`

## Array Abstraction Considerations

Although Size does return a result when the number of dimensions of an array changes, this function does not strictly obey the *law of array abstraction*. This is because it operations over all indexes that are present, rather than only over a set of explicit specified indexes. Because of this, if used inappropriately within a model, incorrect results from Parametric Analyses could result.

In this context, use of Size to find the length of an index or the length of the implicit dimension is a usage that is consistent with the law of array abstraction.

## Notes

Inside a dynamic loop, `Size(Time)`

returns 1. This occurs because in a value context within a dynamic loop, the expression `Time`

(or `@Time`

) evaluates to the current time point (or time position), not the full array of time values. Since there is only one time point at a time in a dynamic loop, the size is 1.

This case is worth remembering since it can be kind of confusing when you (incorrectly) attempt to use `@Time/Size(Time)`

to compute progress, which of course does not produce the desired result. The remedy here is to remember to use `IndexLength(Time)`

or `Size(IndexValue(Time))`

to obtain the index length.

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