Slice a list for a new column in a data.table in R

Question

I am having a data.table with a tab separated string that I want to separate into new columns. However, if I slice by index, I just get the first element of the first row for every field. How do I do this?

library(data.table)
a <- c("feature1\titem1\titem2")
dt1 <- data.table(a)
a <- c("feature2\titem3\titem4")
dt2 <- data.table(a)
dt <- rbindlist(list(dt1, dt2))
dt[, split := mapply(str_split, a, "\t", n = 2)]
# how to get a feature column from that?

https://tidyr.tidyverse.org/reference/separate.html provides one method — Paul Stafford Allen, Nov 29 '22 at 09:07
You're looking for `tstrsplit`, e.g. `dt[, tstrsplit(a, '\t')]` — arg0naut91, Nov 29 '22 at 09:18
But `tstrsplit` does not have an option to only split on the first occurrence like `str_split`, does it? — gernophil, Nov 29 '22 at 10:58

score 0 · Accepted Answer · answered Nov 29 '22 at 09:13

0

One possible solution with transpose:

dt[, transpose(stringr::str_split(a,"\t"))]
         V1     V2     V3
     <char> <char> <char>
1: feature1  item1  item2
2: feature2  item3  item4

answered Nov 29 '22 at 09:13

Waldi

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with `dt[, transpose(stringr::str_split(a, "\t", n = 2))]` it works. Thanks for that :). – gernophil Nov 29 '22 at 10:59

Slice a list for a new column in a data.table in R

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