Question

Sometimes when I am running lots of long programs I think it would be nice if there was a statement or command I could add to the bottom of a file that would tell me whether R returned any error messages (or warning messages) while running a file.

I always scroll up through all of the code to visually check for error messages or warnings and keep thinking it would be nice if R simply told me at the bottom of the code whether any error messages or warnings occurred.

Can R do that? I suppose even if R can do that I would need a while to develop trust in the command line to catch all error messages or warning messages.

With SAS I used to use the find command and search the log window for the word ‘Error’ or ‘Warning’.

Thanks for any thoughts or advice about this.

Here is a very simple example of R code that returns 3 error messages.

x <- c(1,2,3,4)
y <- c(3,4)
z <- x / y
zz
a <- matrix(x, nrow=2, byrow=T)
b <- matrix(x, nrows=2, byrow=T)
z x a
z * a

Answer 1

I assume you are running from a GUI, where errors are not fatal. Here is a solution making use of options(error). The error handler is replaced by a function that increments a variable:

.error.count <- 0
old.error.fun <- getOption("error")
new.error.fun <- quote(.error.count <- .error.count + 1)
options(error = new.error.fun)

### your code here ###
x <- c(1,2,3,4)
y <- c(3,4)
z <- x / y
zz
a <- matrix(x, nrow=2, byrow=T)
b <- matrix(x, nrows=2, byrow=T)
z x a
z * a
######################

cat("ERROR COUNT:", .error.count, "\n")
options(error = old.error.fun)
rm(.error.count, old.error.fun, new.error.fun)