Given a vector of variables of interest for students in a single school, extracts a single value for the school
agg(x)
A single value of the same type as the input vector.
a vector containing student-level observations for a school. If it is a factor it must contain only a single level.
Luke Keele, Penn State University, ljk20@psu.edu
Sam Pimentel, University of California, Berkeley, spi@berkeley.edu
If the input is numeric, agg
returns the mean; if the input is not
numeric, an error will be thrown unless all values are the same, in which
case the single unique value will be returned.