I am having an issue: I am running a loop to process multiple files. My matrices are enormous and therefore I often run out of memory if I am not careful.
Is there a way to break out of a loop if any warnings are created? It just keeps running the loop and reports that it failed much later... annoying. Any ideas oh wise stackoverflow-ers?!
You can turn warnings into errors with:
options(warn=2)
Unlike warnings, errors will interrupt the loop. Nicely, R will also report to you that these particular errors were converted from warnings.
j <- function() {
for (i in 1:3) {
cat(i, "\n")
as.numeric(c("1", "NA"))
}}
# warn = 0 (default) -- warnings as warnings!
j()
# 1
# 2
# 3
# Warning messages:
# 1: NAs introduced by coercion
# 2: NAs introduced by coercion
# 3: NAs introduced by coercion
# warn = 2 -- warnings as errors
options(warn=2)
j()
# 1
# Error: (converted from warning) NAs introduced by coercion
R allows you to define a condition handler
x <- tryCatch({
warning("oops")
}, warning=function(w) {
## do something about the warning, maybe return 'NA'
message("handling warning: ", conditionMessage(w))
NA
})
which results in
handling warning: oops
> x
[1] NA
Execution continues after tryCatch; you could decide to end by converting your warning to an error
x <- tryCatch({
warning("oops")
}, warning=function(w) {
stop("converted from warning: ", conditionMessage(w))
})
or handle the condition gracefully (continuing evaluation after the warning call)
withCallingHandlers({
warning("oops")
1
}, warning=function(w) {
message("handled warning: ", conditionMessage(w))
invokeRestart("muffleWarning")
})
which prints
handled warning: oops
[1] 1
Set the global warn option:
options(warn=1) # print warnings as they occur
options(warn=2) # treat warnings as errors
Note that a "warning" is not an "error". Loops don't terminate for warnings (unless options(warn=2)).
