How do I time out a lapply when a list item fails or takes too long?

Question

For several efforts I\'m involved in at the moment, I am running large datasets with numerous parameter combinations through a series of functions. The functions have a wrap

Answer 1

You may well be able to manage graceful-exits-upon-timout using a combination of tryCatch() and evalWithTimeout() from the R.utils package. See also this post, which presents similar code and unpacks it in a bit more detail.

require(R.utils)

myFun <- function(x) {Sys.sleep(x); x^2}

## evalWithTimeout() times out evaluation after 3.1 seconds, and then
## tryCatch() handles the resulting error (of class "TimeoutException") with 
## grace and aplomb.
myWrapperFunction <- function(i) {
    tryCatch(expr = evalWithTimeout(myFun(i), timeout = 3.1), 
             TimeoutException = function(ex) "TimedOut")
}

sapply(1:5, myWrapperFunction)
# [1] "1"        "4"        "9"        "TimedOut" "TimedOut"