I'm interested in testing whether or not a character string is numeric or
not as follows:

is.na(as.numeric('3')) # returns F
is.na(as.numeric('A')) # I'd like this to return T without issuing a warning
about NAs introduced by coercion.

I guess you could suppress the warning with options(warn=-1), but I was
wondering if there's an alternative.  Or perhaps an alternative that doesn't
use as.numeric()?

Thanks,
Andrew

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