On 28/01/2010 5:30 AM, Benilton Carvalho wrote:
Hi Duncan,
On Tue, Jan 26, 2010 at 9:09 PM, Duncan Murdoch <murd...@stats.uwo.ca> wrote:
On 26/01/2010 3:25 PM, Blanford, Glenn wrote:
Has there been any update on R's handling large integers greater than 10^9
(between 10^9 and 4x10^9) ?
as.integer() in R 2.9.2 lists this as a restriction but doesnt list the
actual limit or cause, nor if anyone was looking at fixing it.
Integers in R are 4 byte signed integers, so the upper limit is 2^31-1.
That's not likely to change soon.
But in the hypothetical scenario that this was to change soon and we
were to have 64bit integer type (say, when under a 64 bit OS),
wouldn't this allow us to have objects whose length exceeded the
2^31-1 limit?
Those are certainly related problems, but you don't need 64 bit integers
to have longer vectors. We could switch to indexing by doubles in R
(though internally the indexing would probably be done in 64 bit ints).
A problem with exposing 64 bit ints in R is that they break the rule
that doubles can represent any integer exactly. If x is an integer, x+1
is a double, and it would be unfortunate if (x+1) != (x+1L), as will
happen with values bigger than 2^52.
Duncan Murdoch
Benilton Carvalho
The double type in R can hold exact integer values up to around 2^52. So for
example calculations like this work fine:
x <- 2^50
y <- x + 1
y-x
[1] 1
Just don't ask R to put those values into a 4 byte integer, they won't fit:
as.integer(c(x,y))
[1] NA NA
Warning message:
NAs introduced by coercion
Duncan Murdoch
Glenn D Blanford, PhD
<mailto:glenn.blanf...@us.army.mil>
Scientific Research Corporation
gblanf...@scires.com<mailto:gblanf...@scires.com>
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