Transform dataframe by grouping row

Question

d1 <- data.frame(Gender=c(\'M\', \'M\', \'M\', \'M\', \'F\', \'F\', \'F\',\'F\'), Age=c(15,38,17,35,26,24,20,26))

And I\'d like to transform it to look l

Answer 1

I'll add the requisite plyr based solution:

library("plyr")
ddply(d1, .(Gender), summarize, Age = paste(Age, collapse = ", "))
##   Gender            Age
## 1      F 26, 24, 20, 26
## 2      M 15, 38, 17, 35