Group value in range r

Question

I have my table(input)

name   value
Rob    35
Helen  20
Sergey 16
Linn   40
Elena  23
Mary   40

And I want to count how many of my users is

Answer 1

We can use

library(data.table)
setDT(input)[,.(num=.N) ,
  .(range=cut(value, breaks = c(0,20, 30, Inf), labels = c("0-20", "21-30", "30-")))]