How to replace certain rows in a data frame without using a for loop

Question

I'd like to replace certain rows of my variable group with blank. How can I do it without using a for loop? Here is my code. The goal is to code 'group' to be: "A", blank, blank, blank, blank, "A", blank, blank...

group <- rep("A", 20)
var   <- rep("B", 20)

out <- data.frame(group, var)

out$row_num <- seq(1:nrow(out))
    
for (i in 1:nrow(out)) {
   if (out$row_num[i] %% 5 != 1) {
      out$group[i] <- " "
    } 
}

Yes, correct. I've fixed it. Thanks!

Ketty
– Ketty

2020-06-30 19:48:26 +00:00
Commented Jun 30, 2020 at 19:48 — Ketty
– Ketty, Commented Jun 30, 2020 at 19:48

akrun · Accepted Answer · 2020-06-30 19:50:03Z

1

These operations are vectorized. So, the replacement can be done without a for loop. Also, from R 4.0, the default option while constructing data.frame is stringsAsFactors = FALSE

out$group[out$row_num %% 5 != 1] <- ' '

Based on the update, if the intention is to replicate

rep(c("A", "", "", "", ""), length.out = 20)
#[1] "A" ""  ""  ""  ""  "A" ""  ""  ""  ""  "A" ""  ""  ""  ""  "A" ""  ""  ""  ""

edited Jun 30, 2020 at 19:50

answered Jun 30, 2020 at 19:27

akrun

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1 Comment

Ketty Over a year ago

Yes, that's what I intend to replicate.

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