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

Given the other answers supplied, I suspect that it is impossible tough to do in exactly the way you specify.

However, I believe there is a way of getting very close, if you use the plyr package creatively. The trick is to use l_ply which takes a list as input and creates no output.

The only real differences between this solution and your specification is that in a for loop you can directly modify variables in the same environment. Using l_ply you need to send a function, so you will have to be more careful if you want to modify stuff in the parent environment.

Try the following:

library(plyr)
forp <- function(i, .fun){
  l_ply(i, .fun, .progress="tk")
}

a <- 0
forp(1:100, function(i){
  Sys.sleep(0.01)
  a<<-a+i
  })
print(a)
[1] 5050

This creates a progress bar and modifies the value of a in the global environment.

---

EDIT.

For the avoidance of doubt: The argument .fun will always be a function with a single argument, e.g. .fun=function(i){...}.

For example:

for(i in 1:10){expr} is equivalent to forp(1:10, function(i){expr})

In other words:

• i is the looping parameter of the loop
• .fun is a function with a single argument i