GroupStat function in customGroupFormat function.

If i try using the groupStat function as mentioned in the page,[]=groupby#math_operations_in_group-by_mode

it is giving me error as

grid.groupStat is not a function.

Is this the version problem or do i need to include a specific js for this?

i have already included the dhtmlxgrid_group.js and dhtmlxgrid_filter.js files.

Also, the two parameter form of groupBy function, the one in which we can include the stat functions, is it present in 2.0 version of grid?  Beacuse, it doesnt seem to work for me.

Math operations in groupBy() is not available in dhtmlxGrid 2.0.