What is integer overflow in R and how can it happen?

Question

I have some calculation going on and get the following warning (i.e. not an error):

Warning messages:
1: In sum(myvar, na.rm = T) :
Integer overflow - use s         


        

Answer 1

What's the max length of integer or numeric?

Vectors are currently indexed with an integer, so the max length is given by .Machine$integer.max. As DWin noted, all versions of R currently use 32-bit integers, so this will be 2^31 - 1, or a little over 2 billion.

Unless you are packing some serious hardware (or you are reading this in the future; hello from 2012) you won't have enough memory to allocate vectors that long.

I remember a discussion where R-core (Brian Ripley, I think) suggested that the next step could be to index vectors with the mantissa of doubles, or something clever like that, effectively giving 48-bits of index. Sadly, I can't find that discussion.

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In addition to the Rmpfr package, if you are suffering integer overflow, you might want to try the int64 package.