Question

How can I use which function in R

Answer 1

which() function determines the position of elements in a logical vector that are TRUE. 

In the below example, we are finding the row number wherein the maximum value of variable v1 is recorded.

mydata=data.frame(v1 = c(2,4,12,3,6))
which(mydata$v1==max(mydata$v1))

It returns 3 as 12 is the maximum value and it is at the 3rd row in the variable x=v1.