r: repeat each value and add a additional string

Question

I need following: repeat two values, each 3 times: I can do it with

rplcts = rep(c("Trt","Ctl"), each=3)

but I also want to add to each string in one group following values: 1,2,3 so, at the end I need this:

"Ctl1" "Ctl2" "Ctl3" "Trt1" "Trt2" "Trt3"

Is there a smart way to do it in r?

paste0(rep(c("Trt","Ctl"), each=3), c(1, 2, 3))?

nrussell
– nrussell

2015-11-25 14:01:26 +00:00
Commented Nov 25, 2015 at 14:01 — nrussell
– nrussell, Commented Nov 25, 2015 at 14:01
paste0(rplcts, 1:3)

G. Grothendieck
– G. Grothendieck

2015-11-25 14:02:07 +00:00
Commented Nov 25, 2015 at 14:02 — G. Grothendieck
– G. Grothendieck, Commented Nov 25, 2015 at 14:02

Benjamin · Accepted Answer · 2015-11-25 14:12:12Z

1

You essentially only need to paste two vectors.

paste0(rep(c("Trt", "Ctl"), each = 3), rep(1:3, 2))

A more general solution could be

mySeq <- function(groups, each){ paste0(rep(groups, each=each), 1:each) # Element recycling will match the length } mySeq(c("Trt", "Ctl"), 3)

edited Nov 25, 2015 at 14:12

answered Nov 25, 2015 at 14:03

Benjamin

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3 Comments

Heroka Over a year ago

Due to element-recycling, you could omit the second call to rep.

Benjamin Over a year ago

I often avoid taking advantage of recycling because I'm terrified of what happens when the one vector's length isn't a multiple of the other's length. But in the controlled state of that function, I think it works nicely. Good catch.

Heroka Over a year ago

I agree with you (better safe than sorry), but in this very controlled case it's acceptable.

bramtayl · Accepted Answer · 2015-11-25 15:30:08Z

Here is is with handy magrittr syntax:

library(magrittr) c("Trt", "Ctl") %>% rep(each = 3) %>% paste0(c(1, 2, 3))

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