Re: [R] Integer precision etc.
On Wed, 2003-08-13 at 07:55, [EMAIL PROTECTED] wrote: > Hi Folks, > With a bit of experimentation I have determined (I think) > that on my R implementation the largest positive integer > that is exactly represented is (2^53 - 1), based on > > > (((2^53)-1)+1) - ((2^53)-1) > [1] 1 > > ((2^53)+1) - (2^53) > [1] 0 > > System: > platform i686-pc-linux-gnu > arch i686 > os linux-gnu > system i686, linux-gnu > status > major1 > minor6.1 > year 2002 > month11 > day 01 > language R > > Is there any other way to determine this sort of information? > > With thanks, > Ted. Ted, See ?.Machine No experimentation required :-) HTH, Marc Schwartz __ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
Re: [R] Integer precision etc.
(Ted Harding) <[EMAIL PROTECTED]> writes: > With a bit of experimentation I have determined (I think) > that on my R implementation the largest positive integer > that is exactly represented is (2^53 - 1), based on > > > (((2^53)-1)+1) - ((2^53)-1) > [1] 1 > > ((2^53)+1) - (2^53) > [1] 0 Those "integer" values are being silently converted to double precision so what you are determining is the relative machine precision for doubles. Use .Machine$integer.max instead. On your platform it will probably be 2^31-1 > .Machine$integer.max [1] 2147483647 > log(.Machine$integer.max, 2) [1] 31 > 2^31-1 [1] 2147483647 > log(.Machine$double.eps, 2) [1] -52 > log(.Machine$double.neg.eps, 2) [1] -53 __ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
RE: [R] Integer precision etc.
1e100 is just one example of much bigger number that is exactly
represented
(in floating point). But of course
> 1e100+1 - 1e100
[1] 0
You mean the biggest number such that adding one changes the result?
I should be extremely careful with
> print( 9007199254740994, digits=20)
[1] 9007199254740994
> print( 9007199254740994-1, digits=20)
[1] 9007199254740992
Here subtracting one makes a difference of two ... but the numbers look
like
integers.
Simon Fear
Senior Statistician
Syne qua non Ltd
Tel: +44 (0) 1379 69
Fax: +44 (0) 1379 65
email: [EMAIL PROTECTED]
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[R] Integer precision etc.
Hi Folks, With a bit of experimentation I have determined (I think) that on my R implementation the largest positive integer that is exactly represented is (2^53 - 1), based on > (((2^53)-1)+1) - ((2^53)-1) [1] 1 > ((2^53)+1) - (2^53) [1] 0 System: platform i686-pc-linux-gnu arch i686 os linux-gnu system i686, linux-gnu status major1 minor6.1 year 2002 month11 day 01 language R Is there any other way to determine this sort of information? With thanks, Ted. E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 167 1972 Date: 13-Aug-03 Time: 13:55:25 -- XFMail -- __ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
Re: [R] Integer precision etc.
On Wed, 13 Aug 2003 [EMAIL PROTECTED] wrote: > Hi Folks, > With a bit of experimentation I have determined (I think) > that on my R implementation the largest positive integer > that is exactly represented is (2^53 - 1), based on > > > (((2^53)-1)+1) - ((2^53)-1) > [1] 1 > > ((2^53)+1) - (2^53) > [1] 0 > The variable .Machine contains this sort of thing. The largest exactly represented integer is .Machine$integer.max and the largest integer exactly represented as a double will be 2^.Machine$double.digits-1 I believe the floating point formats are the same on all versions of R at the moment (though the integer formats might not be) -thomas __ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
RE: [R] Integer precision etc.
Thanks to James Holtman for the confirmation of the IEEE definition, and to Marc Schwartz and Roger Koenker for pointing out ".Machine" which I had not been aware of! For the latter, the information I wanted is in > .Machine$double.digits [1] 53 so that the largest integer exactly represented is indeed 2^53 -1. Best wishes to all, Ted. E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 167 1972 Date: 13-Aug-03 Time: 14:48:48 -- XFMail -- __ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
