In R, how do I add a max by group?
r
Solution
Try
# This is how you create your data.frame
group<-c("A","A","A","A","A","B","B","C","C","C")
replicate<-c(1,2,3,4,5,1,2,1,2,3)
x<-data.frame(group,replicate) # here you don't need c()
# Here's my solution
Max <- tapply(x$replicate, x$group,max)
data.frame(x, max.per.group=rep(Max, table(x$group)))
group replicate max.per.group
1 A 1 5
2 A 2 5
3 A 3 5
4 A 4 5
5 A 5 5
6 B 1 2
7 B 2 2
8 C 1 3
9 C 2 3
10 C 3 3
Problem
I would like to use R to create a new column in my dataset that includes a maximum for each unique group. My data look like this: ``` group<-c("A","A","A","A","A","B","B","C","C","C") replicate<-c(1,2,3,4,5,1,2,1,2,3) x<-data.frame(cbind(group,replicate)) ``` I'd like to create the third column as shown below - the maximum for each group. ``` group replicate max.per.group A 1 5 A 2 5 A 3 5 A 4 5 A 5 5 B 1 2 B 2 2 C 1 3 C 2 3 C 3 3 ```