Thatis was not my original question. My original questions was how memory is managed/allocated in R?
On Thu, Dec 10, 2009 at 6:08 PM, jim holtman <jholt...@gmail.com> wrote: > If you really want to code like a C++ coder in R, then create your own > object and extend it when necessary: > > # take a variation of this; preallocate and then extend when you read a > limit > x <- numeric(2) > for (i in 1:100){ > if (i > length(x)){ > # double the length (or whatever you want) > length(x) <- length(x) * 2 > } > x[i] <- i > } > > On Thu, Dec 10, 2009 at 11:30 AM, Peng Yu <pengyu...@gmail.com> wrote: >> >> I have a situation that I can not predict the final result's dimension. >> >> In C++, I believe that the class valarray could preallocate some >> memory than it is actually needed (maybe 2 times more). The runtime >> for a C++ equivalent (using append) to the R code would still be C*n, >> where C is a constant and n is the length of the vector. However, if >> it just allocate enough memory, the run time will be C*n^2. >> >> Based on your reply, I suspect that R doesn't allocate some memory >> than it is currently needed, right? >> >> On Fri, Dec 11, 2009 at 11:22 AM, Henrik Bengtsson <h...@stat.berkeley.edu> >> wrote: >> > Related... >> > >> > Rule of thumb: >> > Pre-allocate your object of the *correct* data type, if you know the >> > final dimensions. >> > >> > /Henrik >> > >> > On Thu, Dec 10, 2009 at 8:26 AM, Peng Yu <pengyu...@gmail.com> wrote: >> >> I'm wondering where I can find the detailed descriptions on R memory >> >> management. Understanding this could help me understand the runtime of >> >> R program. For example, depending on how memory is allocated (either >> >> allocate a chuck of memory that is more than necessary for the current >> >> use, or allocate the memory that is just enough for the current use), >> >> the performance of the following program could be very different. >> >> Could somebody let me know some good references? >> >> >> >> unsorted_index=NULL >> >> for(i in 1:100) { >> >> unsorted_index=c(unsorted_index, i) >> >> } >> >> unsorted_index >> >> >> >> ______________________________________________ >> >> R-help@r-project.org mailing list >> >> 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. >> >> >> > >> >> ______________________________________________ >> R-help@r-project.org mailing list >> 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. > > > > -- > Jim Holtman > Cincinnati, OH > +1 513 646 9390 > > What is the problem that you are trying to solve? > ______________________________________________ R-help@r-project.org mailing list 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.