Re: [R] calculate differences - strange outcome
Em Qui, 2008-07-17 às 11:47 +0200, Kunzler, Andreas escreveu: Dear List, I ran into some trouble by calculating differences. For me it is important that differences are either 0 or not. So I don't understand the outcome of this calculation 865.56-(782.86+0+63.85+18.85+0) [1] -1.136868e-13 I run R version 2.71 on WinXP Hi Andreas Kunzler, Your problem is cause by numeric represntation in computer (Floating-Point numbers) and this topic is explain in R FAQ 7.31 But the solution for your calculations is possible using the guard digits approach, so if you needd solve: 865.56-(782.86+0+63.85+18.85+0) Using 865.56/100 -(782.86+0+63.85+18.85+0)/100 More details in http://docs.sun.com/source/806-3568/ncg_goldberg.html (This links is indicated in R FAQ 7.31) -- Bernardo Rangel Tura, M.D,MPH,Ph.D National Institute of Cardiology Brazil __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
[R] calculate differences - strange outcome
Dear List, I ran into some trouble by calculating differences. For me it is important that differences are either 0 or not. So I don't understand the outcome of this calculation 865.56-(782.86+0+63.85+18.85+0) [1] -1.136868e-13 I run R version 2.71 on WinXP I could solve my problem by using round() but I would like to know the reason. Maybe someone can help me? Thanx __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] calculate differences - strange outcome
On Thu, 17 Jul 2008 11:47:42 +0200 Kunzler, Andreas [EMAIL PROTECTED] wrote: I ran into some trouble by calculating differences. For me it is important that differences are either 0 or not. If that is the case, restrict yourself to calculating with integers. :) So I don't understand the outcome of this calculation 865.56-(782.86+0+63.85+18.85+0) [1] -1.136868e-13 I run R version 2.71 on WinXP I could solve my problem by using round() but I would like to know the reason. Maybe someone can help me? FAQ 7.31 and the reference cited therein should shed light on your problem. Best wishes, Berwin === Full address = Berwin A TurlachTel.: +65 6516 4416 (secr) Dept of Statistics and Applied Probability+65 6516 6650 (self) Faculty of Science FAX : +65 6872 3919 National University of Singapore 6 Science Drive 2, Blk S16, Level 7 e-mail: [EMAIL PROTECTED] Singapore 117546http://www.stat.nus.edu.sg/~statba __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] calculate differences - strange outcome
Hi Andreas, It's because you are dealing with binary or floating point calculations, not just a few apples and oranges, or an abacus (which, by the way, is an excellent calculating device, and still widely used in some [sophisticated] parts of the world). http://en.wikipedia.org/wiki/Floating_point HTH, Marks. Kunzler, Andreas wrote: Dear List, I ran into some trouble by calculating differences. For me it is important that differences are either 0 or not. So I don't understand the outcome of this calculation 865.56-(782.86+0+63.85+18.85+0) [1] -1.136868e-13 I run R version 2.71 on WinXP I could solve my problem by using round() but I would like to know the reason. Maybe someone can help me? Thanx __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- View this message in context: http://www.nabble.com/calculate-differences---strange-outcome-tp18505010p18505498.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] calculate differences - strange outcome
Kunzler, Andreas wrote: Dear List, I ran into some trouble by calculating differences. For me it is important that differences are either 0 or not. So I don't understand the outcome of this calculation 865.56-(782.86+0+63.85+18.85+0) [1] -1.136868e-13 I run R version 2.71 on WinXP I could solve my problem by using round() but I would like to know the reason. Maybe someone can help me? This is FAQ 7.31. Duncan Murdoch __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
