joining strings in a table according to values in another column

Question

I got a table like this:

id     words
1     I like school.
2     I hate school.
3     I like cakes.
1     I like cats.

Here's what I want to do, joining the strings in each row according to id.

id    words
1    I like school. I like cats.
2    I hate school.
3    I like cakes.

Is there a package to do that in R?

What have you already tried? Where did you get stuck? – paljenczy Jan 16 '16 at 14:19 — paljenczy, Jan 16 '16 at 14:19

score 1 · Accepted Answer · answered Jan 16 '16 at 14:20

We can paste the 'words' together grouped by 'id'. This can be done with any of the group by operations. One way it is data.table. We convert the 'data.frame' to 'data.table' (setDT(df1)) and then do the operation was mentioned above.

# install.packages(c("data.table"), dependencies = TRUE)
library(data.table)
setDT(df1)[, list(words = paste(words, collapse=' ')), by = id]

A base R operation would be to use aggregate

aggregate(words~id, df1, FUN= paste, collape=' ')

joining strings in a table according to values in another column

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