Aggregate by factor levels, keeping other variables in the resulting data frame

Question

I\'m trying to calculate the minimum values of a numeric column for each level of a factor, while keeping values of another factor in the resulting data frame.

Answer 1

If you had added in the index variable that would have done it.

library(plyr)

# ddply
ddply(dat, .(code,index), summarise, val = min(value))

# base R
aggregate(value ~ code + index, dat, min)