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# dim_sum_n_Wrap

Computes the arithmetic sum of a variable's given dimensions at all other dimensions and retains metadata.

Available in version 5.1.1 and later.

## Prototype

```load "\$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"

function dim_sum_n_Wrap (
x        : numeric,
dims [*] : integer
)

return_val  :  float or double
```

## Arguments

x

A variable of numeric type and any dimensionality.

dims

The dimension(s) of x on which to calculate the sum. Must be consecutive and monotonically increasing.

## Return value

The output will be double if x is double, and float otherwise.

The output dimensionality will be the same as all but the dims's dimensions of the input variable. The dimension rank of the input variable will be reduced by the rank of dims.

## Description

The dim_sum_n_Wrap function computes the sum of all elements of the dimensions indicated by dims for each index of the remaining dimensions and retains metadata. A wrapper function. Missing values are ignored.

## Examples

Example 1

Create a variable, q, of size (3,5,10) array. Then calculate the sum of the rightmost dimension.

```    q   = random_uniform(-20,100,(/3,5,10/))
qav = dim_sum_n(q,2)   ;==>  qav(3,5)
```
Example 2

Let x be of size (ntim,nlat,mlon) and with named dimensions "time", "lat" and "lon", respectively. Then, for each time and latitude, the zonal sum (i.e., sum of all non-missing longitudes) is:

```    xSumLon = dim_sum_n( x, 2 )    ; ==> xSumLon(ntim,nlat)
```
Generally, users prefer that the returned variable have metadata associated with it. This can be accomplished via the dim_sum_n_Wrap function:

```    xSumLon = dim_sum_n_Wrap( x,2 )    ; ==> xSumLon(time,lat)
```
Example 3

Let x be defined as in Example 2: x(time,lat,lon). Compute the sum over time at each latitude/longitude grid point.

```    xSumTime = dim_sum( x(lat|:, lon|:, time|:) )    ; ==> xSumTime(nlat,nlon)

xSumTime = dim_sum_n( x, 0 )                     ; no reordering needed
```
```    xSumTime = dim_sum_Wrap( x(lat|:, lon|:, time|:) )    ; ==> xSumTime(lat,lon)