On Tue, 23 May 2006, Matthew Dowle 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"
Note that [[ ]] is documented to only ever return one element, so this is invalid. > Is there a way I can obtain the first 10 items of L[[2]] without a memory > copy of L[[2]] ? Use .Call -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ 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
