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Angular Data Grid: Aggregation - Other

This section covers areas of aggregation that don't fit within the other sections of the documentation.

Default Aggregation Function

When columns are dragged to the Values section of the Columns Tool Panel they are assigned the sum aggregation function by default. The default aggregation function can be overridden on a per-column basis using the defaultAggFunc column property.

<ag-grid-angular
    [columnDefs]="columnDefs"
    /* other grid options ... */>
</ag-grid-angular>

this.columnDefs = [
    {
        field: 'gold',
        // allows column to be dragged to the 'Values` section of the Columns Tool Panel 
        enableValue: true,
        // use 'avg' as the default agg func instead of 'sum'  
        defaultAggFunc: 'avg',
    },
];

The following example demonstrates overriding the default agg function. Note the following:

  • The Gold column is configured with defaultAggFunc set to avg.
  • Drag the Gold column to the Values section of the Columns Tool Panel and note that it is assigned the 'avg' function.
  • The Silver column is configured to use a custom aggregation function as its default. Drag the Silver column to the Values section and note that it is assigned the function mySum.
  • Dragging the Bronze column will use sum as the default.

Note that unlike aggFunc you can't pass a custom aggregation function directly to defaultAggFunc, as demonstrated in the previous example, it must be registered first. See Registering Custom Functions for how to do this.

Restricting Aggregation Functions

By default, all functions are available to all value columns. To restrict the aggregation functions available on a value column, use the allowedAggFuncs column property as shown below:

<ag-grid-angular
    [columnDefs]="columnDefs"
    /* other grid options ... */>
</ag-grid-angular>

this.columnDefs = [
    {
        field: 'gold', 
        aggFunc: 'sum',
        // restricts agg functions to be: `sum`, `min` and `max`
        allowedAggFuncs: ['sum', 'min', 'max'],
    }
];

The following example demonstrates restricting the aggregation functions. Note the following:

  • The Gold column is configured with allowedAggFuncs set to ['sum', 'min', 'max'] and only displays these functions in the drop-down list in the Values section column to the of the Columns Tool Panel.
  • The Silver column shows all available agg functions as it hasn't been restricted.

Aggregation API

After the grid is initialised an aggregation can be applied to a column using the following:

  1. Add the columns to the list of value columns via columnApi.addValueColumn(colKey) - the 'sum' aggFunc is used by default.
  2. (Optional) Modify the aggregation function on the column via columnApi.setColumnAggFunc(colKey, aggFunc).

When the grid initialises, any column definitions that have aggFunc set will be automatically added as a value column.

Column Headers

When aggregating, the column headers will include the aggregation function for the column. For example the header 'Bank Balance' will become 'sum(Bank Balance)' if you have the sum aggregation active on the column. To turn this off and display simply 'Bank Balance' then set the grid property suppressAggFuncInHeader.

Empty Aggregation Calls

When providing either Custom Aggregation Functions or Custom Full Row Aggregation then you will see strange calls to these functions where empty lists are provided.

The empty aggregation calls happen in the following two scenarios:

  1. The grid has no data (usually the case when the gird is initially displayed before the application has set data). Aggregating at the root level will request an aggregation of an empty set.
  2. The grid has groups and a filter, such that groups are empty.

Recomputing Aggregates

If the data changes after the aggregation is done, you can tell the grid to recompute the aggregates through the API method refreshClientSideRowModel('aggregate').