On Mar 29, 2011, at 8:46 AM, Jon Clayden wrote: > Dear all, > > I see from some previous threads that support for 64-bit integers in R > may be an aim for future versions, but in the meantime I'm wondering > whether it is possible to read in integers of greater than 32 bits at > all. Judging from ?readBin, it should be possible to read 8-byte > integers to some degree, but it is clearly limited in practice by R's > internally 32-bit integer type: > >> x <- as.raw(c(0,0,0,0,1,0,0,0)) >> (readBin(x,"integer",n=1,size=8,signed=F,endian="big")) > [1] 16777216 >> x <- as.raw(c(0,0,0,1,0,0,0,0)) >> (readBin(x,"integer",n=1,size=8,signed=F,endian="big")) > [1] 0 > > For values that fit into 32 bits it works fine, but for larger values > it fails. (I'm a bit surprised by the zero - should the value not be > NA if it is out of range?
No, it's not out of range - int is only 4 bytes so only 4 first bytes (respecting endianness order, hence LSB) are used. > ) The value can be represented as a double, > though: > >> 4294967296 > [1] 4294967296 > > I wouldn't expect readBin() to return a double if an integer was > requested, but is there any way to get the correct value out of it? Trivially (for your unsigned big-endian case): y <- readBin(x, "integer", n=length(x)/4L, endian="big") y <- ifelse(y < 0, 2^32 + y, y) i <- seq(1,length(y),2) y <- y[i] * 2^32 + y[i + 1L] Cheers, Simon > I > suppose one could read the bytes into a raw vector and then > reconstruct the number manually from that, but is there a more elegant > or built-in solution that I'm not aware of? > > This is R 2.12.1 on Mac OS X.6.7 - .Machine$sizeof.long is 8. > > Many thanks, > Jon > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
