Aggregation

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.

Defining Aggregations

You can define aggregations on columns in the following three ways:

  1. Built In Functions: Out of the box the grid provides sum, min, max, count, avg, first, last. To use one of these, set colDef.aggFunc to the string of the function you require.
  2. User Registered Functions: You can install your own aggregation functions into the grid and reference them as if they were grid provided functions by calling api.addAggFunc(key,func).
  3. Direct Functions: Lastly you can provide a function directly by setting colDef.aggFunc to your custom function. Direct functions do not appear in the toolPanel when selecting functions for your columns.

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.

// Option 1: column that uses the built in 'sum' function colDef1.aggFunc = 'sum'; // Option 2: register aggFunc to grid called 'abc', then reference by name gridOptions.api.addAggFunc('abc', myCustomAggFunc); colDef2.aggFunc = 'abc'; // Option 3: column uses a function directly colDef3.aggFunc = myCustomAggFunc; // this is the function 2 and 3 above are using function myCustomAggFunc(values) { var sum = 0; values.forEach( function(value) {sum += value;} ); return sum; }

Restricting Functions

By default, all functions are available to all value columns. To restrict the functions on a column, use the allowedAggFuncs column property. // define Gold column colDef = { headerName: 'Gold', field: 'gold', // allow gui to set aggregations for this column enableValue: true, // restrict aggregations to sum, min and max allowedAggFuncs: ['sum','min','max'] ... }

Example 1 - Built In Functions

The example below shows simple aggregation using the built in functions. The following should be noted:

  • In order for aggregations to be used, a group column is specified. The example groups by country by setting rowGroup=true for the country column.
  • Column gold, silver, bronze and total all have enableValue=true. This tells the grid to allow the user to select aggregation functions for these columns. Aggregation functions can be selected from the menu and also in the tool panel.
  • The gold, silver, bronze and total columns all have a different aggregation functions active.
  • The gold column has allowedAggFuncs=['sum','min','max'] which restricts the user to selecting only sum, min or max as the aggregation function for this column.
Remember to mark value columns with enableValue=true when using the Tool Panel. Otherwise you won't be able to drag and drop them to the 'Values' section in the Tool Panel.

Example 2 - Custom Aggregation Functions

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 cellRenderer).

    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.

Aggregation API

After the grid is initialised, there are two steps to set an aggregation on a column:

  1. Set the aggregation function on the column via columnApi.setColumnAggFunc(colKey, aggFunc)
  2. Add the columns to the list of value columns via columnApi.addValueColumn(colKey)

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.

Custom Full Row Aggregation

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.

Using colDef.aggFunc is the preferred way of doing aggregations, only use groupRowAggNodes if you cannot achieve what you want as it will make your code more complex and be less likely to work with other grid features eg pivoting.

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: colDef = { field: 'abby', valueGetter: 'data.a + data.b', colId: 'aaa' } Then the result of the aggregation will be stored in data.aaa and not in 'abby'. Most of the time this will not matter for you as the colId will default to the field if colId is missing and it doesn't violate uniqueness. You need to be aware of this, as if you store the result in a place other than the colId, it won't work.

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.

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').