quick tips: within function assignment and specific object removal

January 31, 2012
By

(This article was first published on mintgene » R, and kindly contributed to R-bloggers)

If you’re familiar with the faster iterations on objects such as lapply, sapply, or apply for matrices, you might get surprised that the function call saves new assignments only locally.

# to assign global variable within function use "<<-" operator
lapply(1:10, function(i) {
    if (i != 1) {
        global.var <<- global.var + i; return(NULL)
    } else {
        global.var <<- i; return(NULL)
    }
})

cat(global.var)
# 55

# another neat trick is the multiple assignment to objects
global.var -> global.var.A -> global.var.B
global.var == global.var.B

# TRUE

One of my favorite lines in R comes from the fact the language environment devours the memory. To focus on particular objects (such as when you need to save it as *.rda), replace the search term within grepl function for the one that you wish to keep.

ls()
# "global.var"   "global.var.A" "global.var.B"

rm(list = ls()[!grepl("global.var.A", ls())])

# refresh memory
gc()

ls()
#  "global.var.A"

Cheers, mintgene.


To leave a comment for the author, please follow the link and comment on his blog: mintgene » R.

R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...



If you got this far, why not subscribe for updates from the site? Choose your flavor: e-mail, twitter, RSS, or facebook...

Comments are closed.