My understanding is that Kendo does not support custom aggregates but you can call a function in the footerTemplate. That function then can provide calculations on the data and can even reference kendo defined aggregates. So, for example,
footerTemplate: "<div><b>Range</b> #= computeRange()#</div>"
If this is correct, how would you write the function computeRange? It would use max-min aggregates.
Also, how would you write a computeMedian function?
Thanks in advance for your help.
I've implemented a solution which my help you to use custom aggregate function using groupFooterTemplate.
Link here
http://christfriedbalizou.github.io/kendo-grid-custom-aggregate-function-hack/