React Data GridAggregation - Custom Functions

This section covers how custom aggregation functions can be supplied and used in the grid.

Registering Custom Functions

Custom functions can be registered to the grid by name via the aggFuncs grid option. The functions can then be applied to columns by referencing the function name in the column definition. The default values of "sum", "min", "max", "first", "last", "count" and "avg" can also be overwritten with custom implementations.

The above example demonstrates the following configuration to register a custom "range" function and applies it to the total column:

const [columnDefs, setColumnDefs] = useState([
    { field: 'total', aggFunc: 'range' },
]);
const aggFuncs = useMemo(() => { 
	return {
        'range': params => {
            const values = params.values;
            return values.length > 0 ? Math.max(...values) - Math.min(...values) : null;
        }
    };
}, []);

<AgGridReact
    columnDefs={columnDefs}
    aggFuncs={aggFuncs}
/>

Directly Applied Functions

For columns not Configured via the UI, it can be simpler to directly apply custom functions to columns. This can be done by passing a custom function directly to the column aggFunc property.

The above example demonstrates the following configuration to apply a custom "range" function to the total column:

const [columnDefs, setColumnDefs] = useState([
    {
        field: 'total',
        aggFunc: params => {
            const values = params.values;
            return values.length > 0 ? Math.max(...values) - Math.min(...values) : null;
        }
    }
]);

<AgGridReact columnDefs={columnDefs} />

Multiple Group Levels

When aggregations are applied across multiple levels of grouping, the aggregation function is called recursively. This has the effect where some groups aggregate the results of other aggregations, causing incorrect results.

To handle this, the aggregation function should return an object containing relevant meta data for the next level of aggregation, and a "value" field representing the result for this level.

The above example demonstrates the following configuration to apply a custom "range" function which works with multiple levels of row grouping:

const [columnDefs, setColumnDefs] = useState([
  { field: 'total', aggFunc: 'range' },
  // ... other column definitions
]);
const aggFuncs = useMemo(() => { 
	return {
      range: params => {
        const values = params.values;
        // aggregate leaf rows
        if (params.rowNode.leafGroup) {
            const max = Math.max(...values);
            const min = Math.min(...values);
            return {
                max: max,
                min: min,
                value: max - min,
            }
        }

        // aggregate group rows
        let max = values[0].max;
        let min = values[0].min;
        values.forEach(groupResult => {
            max = Math.max(max, groupResult.max);
            min = Math.min(min, groupResult.min);
        });
        return {
            max: max,
            min: min,
            value: max - min,
        };
      }
    };
}, []);

<AgGridReact
    columnDefs={columnDefs}
    aggFuncs={aggFuncs}
/>

Next Up

Continue to the next section to learn about Total Rows.