Question

Sorry guys if this is a noob question.
I need help on how to loop over my dataframe.Here is a sample data.

a <- c(10:29);
b <- c(40:59);
e <- rep(1,20);
test <- data.frame(a,b,e)

I need to manipulate column “e” using the following criteria for values in column “a”

for all values of

“a” <= 15, “e” = 1,

“a” > 15 & < 20, “e” = 2

“a” > 20 & < 25, “e” = 3

“a” > 25 & < 30, “e” = 4 and so on to look like this

result <- cbind(a,b,rep(1:4, each=5))

My actual data frame is over 100k long. Would be great if you could sort me out here.

Answer 1

data.frame(a, b, e=(1:4)[cut(a, c(-Inf, 15, 20, 25, 30))])

Update:

Greg’s comment provides a more direct solution without the need to go via subsetting an integer vector with a factor returned from cut.

data.frame(a, b, e=findInterval(a, c(-Inf, 15, 20, 25, 30)))