How to calculate median of profits for a particular country

Question

Hello folks, I am new to R and I am trying to compute median profit for a particular country in a data frame.I tried below one but it doesn\'t work for me.

Answer 1

median(Forbes2000$sales[Forbes2000$country == "United States"])

Though it's hard to be certain without knowing what your data frame looks like. If you want to get a data.frame with the median of every country instead of just one, you could do:

library(plyr)
ddply(Forbes2000, "country", function(d) median(d$sales))

(You would have to install the plyr package first, for example by doing install.packages("plyr")).