extract data from only columns matching character strings

Question

I have a dataset that looks something like this (but much larger)

Jul_08 <- c(1,0,2,0,3)
Aug_08 <- c(0,0,1,0,1)
Sep_08 <- c(0,1,0,0,1)
month<-c(\"Jul         


        

Answer 1

You can use matrix indexing:

w <- match(month, names(dataset))

dataset$value <- dataset[ cbind(seq_len(nrow(dataset)), w) ]

Here the w vector tells R which column to take the value from and seq_len is used to say use the same row, so the value column is constructed by taking the 1st column in the 1st row, then the 2nd column and 2nd row, 1st column for the 3rd row, etc.