Wrapper to FOR loops with progress bar

Question

I like to use a progress bar while running slow for loops. This could be done easily with several helpers, but I do like the tkProgressBar from tcl

Answer 1

Thanks for everyone for your kind answers! As none of those fit my wacky needs, I started to steal some pieces of the given answers and made up a quite customized version:

forp <- function(iis, .fun) {
    .fun <- paste(deparse(substitute(.fun)), collapse='\n')
    .fun <- gsub(' <- ', ' <<- ', .fun, fixed=TRUE)
    .fun <- paste(.fun, 'index.current <- 1 + index.current; setTkProgressBar(pb, index.current, label=paste( round(index.current/index.max*100, 0), "% ready!"))', sep='\n')
    ifelse(is.numeric(iis), index.max <- max(iis), index.max <- length(iis))
    index.current <- 1
    pb <- tkProgressBar(title = "Working hard:", min = 0, max = index.max, width = 300) 
    for (i in iis) eval(parse(text=paste(.fun)))
    close(pb)
}

This is quite lengthy for a simple function like this, but depends only on base (anf of course: tcltk) and has some nice features:

• can be used on expressions, not just functions,
• you do not have to use <<- in your expressions to update global environment, <- are replaced to <<- in the given expr. Well,this might be annoying for someone.
• can be used with non-numeric indexes (see below). That is why the code become so long :)

Usage is similar to for except for you do not have to specify the i in part and you have to use i as index in the loop. Other drawback is that I did not find a way to grab the {...} part specified after a function, so this must be included in the parameters.

Example #1: Basic use

> forp(1:1000, {
+   a<-i
+ })
> a
[1] 1000

Try it to see the neat progress bar on your computer! :)

Example #2: Looping through some characters

> m <- 0
> forp (names(mtcars), {
+   m <- m + mean(mtcars[,i])
+ })
> m
[1] 435.69