On Wed, Sep 1, 2010 at 8:09 AM, Tal Galili <tal.gal...@gmail.com> wrote: > Hello all, > > A friend recently brought to my attention that vector assignment actually > recreates the entire vector on which the assignment is performed. > > So for example, the code: > x[10]<- NA # The original call (short version) > > Is really doing this: > x<- replace(x, list=10, values=NA) # The original call (long version) > # assigning a whole new vector to x This has been much discussed on this list. Short answer: R is a functional programming lanugage that uses call by value, not references.
Longer answer: It depends. R will not create a copy if it can avoid it (usually?). Search the list archives for "call by value", "copy arguments", etc. for authoritative answers. -- Bert Gunter Genentech Nonclinical Statistics > Which is actually doing this: > x<- `[<-`(x, list=10, values=NA) # The actual call > > > Assuming this can be explained reasonably to the lay man, my question is, > why is it done this way ? > Why won't it just change the relevant pointer in memory? > > On small vectors it makes no difference. > But on big vectors this might be (so I suspect) costly (in terms of time). > > > I'm curious for your responses on the subject. > > Best, > Tal > > > > ----------------Contact > Details:------------------------------------------------------- > Contact me: tal.gal...@gmail.com | 972-52-7275845 > Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) | > www.r-statistics.com (English) > ---------------------------------------------------------------------------------------------- > > [[alternative HTML version deleted]] > > ______________________________________________ > 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.
