The aggregate operator takes an input array, list of one or more aggregate function calls, and (optionally) a list of dimensions along which the aggregates are to be computed. It returns an array containing the computed aggregate values.

Synopsis

aggregate(array, aggregate_1
[, aggregate_2,... aggregate_N]
[,dimension_1, dimension_2,...]);

Summary

SciDB aggregates are functions of several values that produce a scalar value. Used together with the aggregate and redimension operators, they compute data aggregations, optionally grouped along a specified dimension or dimensions.
The aggregate operator takes the following arguments:

Array name. The aggregation is performed on data from the named array.
Aggregating functions. This is the aggregation to perform. You can list one or more aggregating functions.
Dimensions (optional). Most aggregates allow aggregation along one or more dimensions. You can list zero or more dimensions along which to perform the aggregation.

The aggregate operator returns a SciDB array containing the aggregation result as a new attribute. The name of this attribute is constructed as follows: inputAttribute_aggregateFunction, where:

inputAttribute is the name of the aggregated attribute.
aggregateFunction is the name of the aggregate function called.

For example, assume an array A with an attribute sales. The name for the result attribute of aggregate(A,sum(sales)); is 'sales_sum'.

Example

To create a sparse array and then performs some aggregation on it, do the following:

Create an array containing values along the diagonal, and empty cells everywhere else:

AFL% store(redimension (
                 apply (
                       build(<val:double>[i1=0:3; j1=0:3], i1),
                 i, iif(i1=j1, i1,null), j, iif(i1=j1,i1,null)),
           <val:double>[i=0:3; j=0:3]),A);
{i,j} val
{0,0} 0
{1,1} 1
{2,2} 2
{3,3} 3

Use the aggregate operator to count the number of non-empty cells:
```
AFL% aggregate(A, count(val));
{i} val_count
{0} 4
```
Use the aggregate operator to calculate the sum of all cells in the array:
```
AFL% aggregate(A, sum(val));
{i} val_sum
{0} 6
```

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