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:
Built In Functions: Out of the box the grid provides
sum, min, max, count, avg, first, last. To use one of these, set
colDef.aggFuncto the string of the function you require.
- 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).
Direct Functions: Lastly you can provide a
function directly by setting
colDef.aggFuncto 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.
addAggFuncto register it.
By default, all functions are available to all value columns. To restrict the functions on
a column, use the
allowedAggFuncs column property.
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=truefor 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.
enableValue=truewhen using the Tool Panel. Otherwise you won't be able to drag and drop them to the 'Values' section in the Tool Panel.
Custom Aggregation Functions
It is possible to add your own custom aggregation to the grid. Custom aggregation functions can be applied directly to the column or registered to the grid and reference by name (similar to grid provided functions).
A custom aggregation function takes a list of values and should return the result of the aggregation.
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
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
Sum on Gold: The gold column gets a custom
sumaggregated 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
The sum function is set using a
'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
'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 we also set 'xyz' in the grid options as otherwise the grid would complain 'Function not found' as it tries to use the function before it is set via the API.
Note that custom aggregations will get called for the top level rows to calculate a 'Grand Total', not just for row groups. For example if you have 10 rows in the grid, the grid will still call the aggregation with 10 values to get a grand total aggregation.
The grand total aggregation is normally not seen, unless the grid is configured with Grouping Total Footers. Total footers display the result of the aggregation for top level, for example displaying a grand total even if no row grouping is active.
When the grid is empty, the aggregations are still called once with an empty set. This is to calculate the grand total aggregation for the top level.
Example 3 - Multi-Column Aggregation
The next example shows a ratio calculation to demonstrate how to create an
aggFunc that uses values
from multiple columns.
When values from multiple columns are required, a value object containing all the required values across multiple
columns should be passed around instead of a simple value. This value object should also contain a
toString() method so it can also be resolved by the grid to a single value. This is shown in
the code snippet below:
The following example demonstrates this approach in action:
After the grid is initialised, there are two steps to set an aggregation on a column:
- Set the aggregation function on the column via
- Add the columns to the list of value columns via
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
'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
Custom Full Row Aggregation
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
as a grid callback.
colDef.aggFuncis the preferred way of doing aggregations, only use
groupRowAggNodesif you cannot achieve what you want as it will make your code more complex. Also note that
groupRowAggNodeswill not work when 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:
data.aaa and not in 'abby'. Most of the time this
will not matter for you as the colId, if not provided, will default to the field.
In order for the grid to display the aggregation result, it must be stored in the correct field name.
Below shows an example using
groupRowAggNodes. The example doesn't represent a real world scenario,
it's contrived for 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.
Empty Aggregation Calls
The empty aggregation calls happen in the following two scenarios:
- 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.
- The grid has groups and a filter, such that groups are empty.
If the data changes after the aggregation is done, you can tell the grid to recompute the aggregates
through the api method