[R] Combine by columns a vector with another vector that is constant across rows
Eric Berger
er|cjberger @end|ng |rom gm@||@com
Wed Jul 4 08:32:57 CEST 2018
For what it's worth, for larger vectors, and following on from your
observation that the do.call() approach is faster, the following provides
some modest additional speedup:
cbind(x,t(do.call(cbind, lapply(x, function(y) vec))))
Rgds,
Eric
On Tue, Jul 3, 2018 at 8:12 PM, Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> Thanks for all of the suggestions. I did some benchmarking:
>
> library(microbenchmark)
>
> x <- 1:5
> vec <- c(2,4,3)
>
> fastWolfgang <- function(v, vec)
> matrix(c(v, rep(vec, each = length(v))), nrow = length(v))
>
> microbenchmark(cbind(x, t(replicate(length(x), vec))),
> t(sapply(x, function(x) c(x, vec))),
> do.call(rbind, lapply(x, function(x) c(x, vec))),
> t(mapply(c, x, MoreArgs=list(vec))),
> Reduce(cbind, vec, x),
> Reduce(cbind2, vec, x),
> fastWolfgang(x, vec), times=10000L)
>
> Jeff's approach is fastest, but Gabor's Reduce(cbind, vec, x) is close
> (and I really like its simplicity); and very similar to the do.call()
> approach.
>
> Interestingly, for larger vectors, such as:
>
> x <- 1:50
> vec <- sample(1:100, 200, replace=TRUE)
>
> the do.call() approach is the fastest.
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: Jeff Newmiller [mailto:jdnewmil using dcn.davis.ca.us]
> >Sent: Tuesday, 03 July, 2018 17:48
> >To: r-help using r-project.org; Viechtbauer, Wolfgang (SP); r-help using r-
> >project.org
> >Subject: Re: [R] Combine by columns a vector with another vector that is
> >constant across rows
> >
> >Sorry trying again...
> >
> >fastWolfgang <- function( v, vec ) {
> > matrix( c( v, rep( vec, each = length( v ) ) )
> > , nrow = length( v ) )
> >}
> >
> >On July 3, 2018 8:21:47 AM PDT, Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
> >wrote:
> >>Gabor's solution seems to optimize 'simpler'.
> >>
> >>More efficient is to learn that in R a vector is not a matrix, but a
> >>matrix is just an ornamented vector.
> >>
> >>fastWolfgang <- function( v, vec ) {
> >> matrix( c( v, rep( vec, length( v ) ) )
> >> , now = length( v ) )
> >>}
> >>
> >>On July 3, 2018 6:28:45 AM PDT, "Viechtbauer, Wolfgang (SP)"
> >><wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> >>>Hi All,
> >>>
> >>>I have one vector that I want to combine with another vector and that
> >>>other vector should be the same for every row in the combined matrix.
> >>>This obviously does not work:
> >>>
> >>>vec <- c(2,4,3)
> >>>cbind(1:5, vec)
> >>>
> >>>This does, but requires me to specify the correct value for 'n' in
> >>>replicate():
> >>>
> >>>cbind(1:5, t(replicate(5, vec)))
> >>>
> >>>Other ways that do not require this are:
> >>>
> >>>t(sapply(1:5, function(x) c(x, vec)))
> >>>do.call(rbind, lapply(1:5, function(x) c(x, vec)))
> >>>t(mapply(c, 1:5, MoreArgs=list(vec)))
> >>>
> >>>I wonder if there is a simpler / more efficient way of doing this.
> >>>
> >>>Best,
> >>>Wolfgang
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