Count comma delimited values and replicate a value equal times in R

Question

Given the following example data ...

id                               Proteins
522     Q9UHC7-4;Q9UHC7-3;Q9UHC7-2;Q9UHC7
523                                Q9UHV7
524                       Q9Y6T7-2;Q9Y6T7
525                       Q9Y6T7-2;Q9Y6T7

... I would like to create a third column with each id times the number of semicolon delimited values of each row. More specifically something like that:

id                               Proteins     newCol
522     Q9UHC7-4;Q9UHC7-3;Q9UHC7-2;Q9UHC7    522;522;522;522
523                                Q9UHV7    523
524                       Q9Y6T7-2;Q9Y6T7    524;524
525                       Q9Y6T7-2;Q9Y6T7    525;525

I have tried this dt$newCol <- rep(dt$id, lengths(str_split(dt$Proteins, ";"))) but doesn't work since it creates a longer list.

Answer 1

Something like this?

library(stringr)
df$newCol <- str_replace_all(df$Proteins, "[^;]+", as.character(df$id))

Output

> df
   id                          Proteins          newCol
1 522 Q9UHC7-4;Q9UHC7-3;Q9UHC7-2;Q9UHC7 522;522;522;522
2 523                            Q9UHV7             523
3 524                   Q9Y6T7-2;Q9Y6T7         524;524
4 525                   Q9Y6T7-2;Q9Y6T7         525;525

---

Another Base R solution suggested by @markus

df1$new <- Map(gsub, pattern = "[^;]+", replacement = df1$id, x = df1$Proteins)