This function returns a data.frame with the number of students
and number de actions (min-max) aggregated by a specific variable.
Arguments
data
A matrix or data.frame
id.var
a vector with the individuals identification. It is a
quo() type.
var.group
a vector with the group variable. It is a quo() type.
save.table
if TRUE, will save the table generated as an object
of class data.frame. Otherwise, will print the table in pandoc
format, but the object will not be saved (even if the user assigns it to an object)