On Tue, Aug 28, 2012 at 1:37 PM, R. Michael Weylandt <[email protected]> wrote: > On Tue, Aug 28, 2012 at 1:29 PM, Sam Steingold <[email protected]> wrote: >> At the end of a for loop its variables are still present: >> >> for (i in 1:10) { >> x <- vector(length=100000000) >> } >> ls() >> >> will print "i" and "x". >> this means that at the end of the for loop body I have to write >> >> rm(x) >> gc() >> >> is there a more elegant way to handle this? > > Wrap the loop in local() scope perhaps? This might get tricky if you > need to save some results from the loop, but I think you're ok if they > are initialized outside the loop and you use super-assignment. Almost > always you shouldn't need manual garbage collection. > > Something like: # Terribly impractical, but gets the point across > > y <- numeric(100) > local({ > for(i in 1:10){ > x <- rnorm(10) > y[10*(i-1) + 1:10] <<- x > } > }) > > print(x) # Error > print(y) > > Doubt that works out to be significantly more elegant however.
Elaborating a little more: the difficulty in this approach is that, if you need results from the loop in a variable (instead of just doing something n times and printing the results), you need R to know which variables you intend to keep and which can be thrown away in the loop: since a loop doesn't define its own scope like some languages (a practice that always seemed strange to me), you have to resort to tricks like `<<-` to move variables outside the local() scope. The other answer is to use functions / apply statements like the good lord and John Chambers intended :-) M > > Michael > >> >> Thanks. >> >> -- >> Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X >> 11.0.11103000 >> http://www.childpsy.net/ http://camera.org http://palestinefacts.org >> http://iris.org.il http://www.PetitionOnline.com/tap12009/ >> http://truepeace.org >> Computers are like air conditioners: they don't work with open windows! >> >> ______________________________________________ >> [email protected] 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. ______________________________________________ [email protected] 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.
