On 5/23/06, Matthew Dowle <[EMAIL PROTECTED]> wrote: > > Hi, > > n = 10000000 > L = list(a=integer(n), b=integer(n)) > > L[[2]][1:10] gives me the first 10 items of the 2nd vector in the list L. > It works fine. However it appears to copy the entire L[[2]] vector in > memory first, before subsetting it. It seems reasonable that "[[" can't > know that all that is to be done is to do [1:10] on the result and therefore > a copy in memory of the entire vector L[[2]] is not required. Only a new > vector length 10 need be created. I see why [[ needs to make a copy in > general. > > L[[c(2,1)]] gives me the 1st item of the 2nd vector in the list L. It > works fine, and does not appear to copy L[[2]] in memory first. Its much > faster as n grows large. > > But I need more than 1 element of the vector .... L[[c(2,1:10)]] fails > with "Error: recursive indexing failed at level 2" > > Is there a way I can obtain the first 10 items of L[[2]] without a memory > copy of L[[2]] ?
I think environments will help you out here: n < 10000000 env <- new.env() env$a <- integer(n) env$b <- integer(n) env$a[1:10] /Henrik > Thanks! > Matthew > > R 2.1.1 > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
