When grouping, you can apply an aggregation function to any column to populate the group row with values. You can pick from the grid's built in aggregation functions or provide your own.
You can define aggregations on columns in the following three ways:
Aggregation functions are provided with an array of values that it should aggregate into one value that it then returns. The following code snippet shows defining aggregations for columns in each of the three ways explained above.
By default, all functions are available to all value columns. To restrict the functions on
a column, use the allowedAggFuncs column property.
The example below shows simple aggregation using the built in functions. The following should be noted:
The next example shows many custom aggregation functions configured in a variety of ways and demonstrating different things aggregation functions can do.
The following can be noted from the example:
Min/Max on Age Column: The function creates an aggregation over age giving a min and a max age. The function knows whether it is working with leaf nodes (original row data items) or aggregated nodes (ie groups) by checking the type of the value. If the value is a number, it's a row data item, otherwise it's a group. This is because the result of the aggregation has two values based on one input value.
The min/max function is then set by placing the function directly as the colDef.aggFunc.
Average on Age Column: The age columns is aggregated a second time with a custom average function. The average function also needs to know if it is working with leaf nodes or group nodes, as if it's group nodes then the average is weighted. The grid also provides an average function that works in the same way, so there is no value in providing your own average function like this, it is done in this example for demonstration purposes.
The average function is also set by placing the function directly as the colDef.aggFunc.
Sum on Gold: The gold column gets a custom sum aggregated function. The new sum function doesn't do anything different to the built in sum function, however it serves as a demonstration on how you can override. Maybe you want to provide a sum function that uses for example the math.js library.
The sum function is set using a gridOptions property.
'123' on Silver: The '123' function ignores the inputs and always returns the value 123. Because it is registered as an aggregation function, it can be reference by name in the column definitions. Having a function return the same thing isn't very useful, however for the example it demonstrates easily where in the grid the function was used.
The '123' function, like 'sum', is set using a gridOptions property.
'xyz' on Bronze:
The 'xyz' function is another function with much use, however it demonstrates you can return anything
from an aggregation function - as long as your aggregation function can handle the result (if you have
groups inside groups) and as long as your cell renderer can render the result (if using
The 'xyz' function is set using the API.
Note that the example below gives an error on the console saying it cannot find 'xyz'. This is because it tries to aggregate the empty set when the grid is been initialised. The same would happen if you set the data via the rowData property. It is because 'xyz' is set after the grid is initialised. To prevent this error you should opt for setting the aggFunc as a grid property (directly into the grid options) or make sure that aggFunc is not used in any column until it is configured into the grid.
After the grid is initialised, there are two steps to set an aggregation on a column:
When the grid initialises, any column definitions that have aggFunc set will be automatically added as a value column.
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.
Using colDef.aggFunc is the preferred way of doing aggregations. However you may find scenarios where you cannot define your aggregations with respect to individual column values. Maybe you are aggregating sales records in different currencies and you need to read the value from one column and the currency code from another column and then convert the record to a common currency for aggregation - the point being you need data from more than just one column, or you want to put the results into different columns to the inputs for the calculation. For that reason, you can take control of the row aggregation by providing a groupRowAggNodes function as a grid callback.
For groups, when aggregating, the grid stores the results in the colId of the column. For example, if you
have a group defined as follows:
Below shows a contrived example using groupRowAggNodes. The example makes no sense, however it serves the demonstration. It takes the number of medals as inputs and creates two outputs, one as a normal sum and another by multiplying the result by Math.PI.
If the data changes after the aggregation is done, you can tell the grid to recompute the aggregates through the
api method recomputeAggregates. For example, if you allow editing,
and want the aggregates to update as new values are edited, then create code like the following: