# Sum

## Sum(x, i)

Returns the sum of array «x» over Index «i».

You can also sum over multiple indexes:

Sum(A, I, J, K)

It is one of a number of Array-reducing functions, so-called because they reduce the number of dimensions (indexes) of an array.

Sum treats any Null values in «x» as zero.  It can also treat NaN or text and other non-numerical values as zero, if you set optional parameters, «ignoreNaN» or «ignoreNonNumbers» to True.

## Example

This example uses Array Function Example Variables.

Sum(Car_prices, Years) →
Car_type ▶
VW Honda BMW
90K 103K 141K

## Optional Parameters

Sum(x: Array[i]; i: ... optional Index; IgnoreNonNumbers, IgnoreNaN: Optional Boolean)
##### IgnoreNaN

Set «ignoreNaN» to treat NaN, indeterminate numeric values, as zero. Normally NaNs propagate through a model -- Sum(x, i) returns NaN if any value in «x» is NaN. This can help tracking down numeric problems in your logic, such as 0/0 or Sqrt(-1). But if you know there are NaNs that you want to ignore, set «ignoreNaN» parameter to True (or 1).

Sum(x, i, ignoreNaN: True)
##### IgnoreNonNumbers

Similarly, set optional parameter «ignoreNonNumbers» to True, to treat non-numeric values such as text or references, as zero, e.g.:

Sum(x, i, j, ignoreNonNumbers: True)

You must use named parameter syntax for «IgnoreNonNumbers» and «IgnoreNaN», as shown in the above examples, because parameter «i» is optional and repeated.

Date-time numbers are not ignored (they are considered numbers).

##### IgnoreDates

New to Analytica 5.3

Set «ignoreDates» to True to (also) ignore date-time numbers.

#### Using Sum to add arrays

With Intelligent Arrays, you can of course add two arrays with the "+" operator:

a1 + a2

You can also Sum to do this:

Sum([a1, a2])

In this example, the «i» parameter is omitted, and it automatically sums over the implicit index of the list [a1, a2]. The difference between this example and simply using the "+" operator is that using Sum treats any Null values as 0, whereas a1 + a2 returns Null if any values to be added are Null.

### Sum over text values

In older releases, Sum concatenates values as text, of any values contain text. This feature hides a common error, when you inadvertently try to sum text values thinking that they are numbers, so we strongly discourage using Sum this way. It still works for backward compatibility with older models, but since release 4.5, it gives a warning.

If you want to sum over the numbers only and ignore the text, use the «ignoreNonNumbers» parameter:

Sum(X, I, IgnoreNonNumbers: True) → 18

If you really want to concatenate text, use the "&" operator or JoinText function instead, to make it clear that's what you want to do.

Example:

X := Array(I, [5, 6, 'X', 7])
IgnoreWarnings(Sum(X, I)) → "11X7"

This sum evaluates (5 + 6 + 'X' + 7) as (((5 + 6) & 'X') & 7). It converts the numbers to text and concatenates them to form "11X7".