Hi all! I have a tibble regarding a series of comments on a forum; the tibble has a certain number of variables, and in particular: id: comment id; author_id: author id; parent_id: if the message is a reply, the original comment id I want to add another column, in which I put the author id of the original comment, when parent_id IS NOT NA. I already tried to use mutate + ifelse but my problem is that I have to refer to an author id in a different row than that in which I'm evaluating the if condition... Thanks in advance, Alessandro [[alternative HTML version deleted]]
# create some test data
df <- data.frame( id=101:105, author_id=25:21, parent_id=c(NA,NA,101,NA,NA)
)
df$parent_author_id <- sapply(1:nrow(df),
function(i) { if( !is.na(df$parent_id[i]) ) { j <-
match(df$parent_id[i],df$id); df$author_id[j] } else NA } )
df
# id author_id parent_id parent_author_id
# 1 101 25 NA NA
# 2 102 24 NA NA
# 3 103 23 101 25
# 4 104 22 NA NA
# 5 105 21 NA NA
HTH,
Eric
On Sun, Jul 7, 2019 at 7:59 AM Alessandro Puglisi <
alessandro.puglisi at gmail.com> wrote:
> Hi all!
>
> I have a tibble regarding a series of comments on a forum; the tibble has a
> certain number of variables, and in particular:
>
> id: comment id;
> author_id: author id;
> parent_id: if the message is a reply, the original comment id
>
> I want to add another column, in which I put the author id of the original
> comment, when parent_id IS NOT NA.
>
> I already tried to use mutate + ifelse but my problem is that I have to
> refer to an author id in a different row than that in which I'm
evaluating
> the if condition...
>
> Thanks in advance,
> Alessandro
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
[[alternative HTML version deleted]]
Can't this be done more simply and efficiently (no sapply implied loops, no
conditionals) just with indexing?
Using Eric's example:
df <-within(df,
parent_author_id <- author_id[match(parent_id, id)]
)
> df
id author_id parent_id parent_author_id
1 101 25 NA NA
2 102 24 NA NA
3 103 23 101 25
4 104 22 NA NA
5 105 21 NA NA
Cheers,
Bert
Bert Gunter
"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Sat, Jul 6, 2019 at 11:33 PM Eric Berger <ericjberger at gmail.com>
wrote:
> # create some test data
> df <- data.frame( id=101:105, author_id=25:21,
parent_id=c(NA,NA,101,NA,NA)
> )
>
> df$parent_author_id <- sapply(1:nrow(df),
> function(i) { if( !is.na(df$parent_id[i]) ) { j <-
> match(df$parent_id[i],df$id); df$author_id[j] } else NA } )
>
> df
>
> # id author_id parent_id parent_author_id
> # 1 101 25 NA NA
> # 2 102 24 NA NA
> # 3 103 23 101 25
> # 4 104 22 NA NA
> # 5 105 21 NA NA
>
> HTH,
> Eric
>
>
> On Sun, Jul 7, 2019 at 7:59 AM Alessandro Puglisi <
> alessandro.puglisi at gmail.com> wrote:
>
> > Hi all!
> >
> > I have a tibble regarding a series of comments on a forum; the tibble
> has a
> > certain number of variables, and in particular:
> >
> > id: comment id;
> > author_id: author id;
> > parent_id: if the message is a reply, the original comment id
> >
> > I want to add another column, in which I put the author id of the
> original
> > comment, when parent_id IS NOT NA.
> >
> > I already tried to use mutate + ifelse but my problem is that I have
to
> > refer to an author id in a different row than that in which I'm
> evaluating
> > the if condition...
> >
> > Thanks in advance,
> > Alessandro
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
[[alternative HTML version deleted]]