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$double.digits [1] 53 so that the largest integer exactly represented is indeed 2^53 -1. Best wishes to all, Ted. E-Mail: (Ted Harding) [EMAIL PROTECTED] Fax-to-email: +44 (0)870 167 1972 Date: 13-Aug-03 Time: 14:48:48 -- XFMail -- __ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
RE: [R] Integer precision etc.
1e100 is just one example of much bigger number that is exactly
represented
(in floating point). But of course
1e100+1 - 1e100
[1] 0
You mean the biggest number such that adding one changes the result?
I should be extremely careful with
print( 9007199254740994, digits=20)
[1] 9007199254740994
print( 9007199254740994-1, digits=20)
[1] 9007199254740992
Here subtracting one makes a difference of two ... but the numbers look
like
integers.
Simon Fear
Senior Statistician
Syne qua non Ltd
Tel: +44 (0) 1379 69
Fax: +44 (0) 1379 65
email: [EMAIL PROTECTED]
web: http://www.synequanon.com
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Re: [R] Integer precision etc.
(Ted Harding) [EMAIL PROTECTED] writes: With a bit of experimentation I have determined (I think) that on my R implementation the largest positive integer that is exactly represented is (2^53 - 1), based on (((2^53)-1)+1) - ((2^53)-1) [1] 1 ((2^53)+1) - (2^53) [1] 0 Those integer values are being silently converted to double precision so what you are determining is the relative machine precision for doubles. Use .Machine$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.
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
