Thanks a lot for your explanation! I see the point and I think I'll solve my question using a different method!
Andreia Leite On Sun, Jun 24, 2012 at 10:53 PM, Oliver Ruebenacker <cur...@gmail.com>wrote: > Hello, > > The FAQ answer 7.31 may be confusing to noobs and the referenced > paper is long. The essence is: > > (1) It's not an R issue, it is a floating point (flop) arithmetic issue. > (2) The issue is that flop arithmetic is almost always only approximate. > (3) Therefore, asking for exact equality of two flops is almost > always a mistake. > (4) In simple cases, you can take the difference of two flops and > ask whether it is good enough > (5) For extended calculations, you need to keep in mind that errors > propagate and accumulate. > (6) Some ill-defined problems may lead to "solutions" that aren't > solutions (e.g. trying to invert a singular matrix) > (7) Some well-defined problems may defy a straight-forward approach > (e.g. solving stiff differential equations) > > Take care > Oliver > > On Sun, Jun 24, 2012 at 5:29 PM, Sarah Goslee <sarah.gos...@gmail.com> > wrote: > > Please read R FAQ 7.31, Why doesn't R think these numbers are equal? > > > > Sarah > > > > On Sun, Jun 24, 2012 at 1:58 PM, Andreia Leite > > <andreiaheitorle...@gmail.com> wrote: > >> Dear list, > >> > >> I'm trying to do a loop where I should choose a cell of a data frame > >> comparing it with another. The code actually works for the majority of > the > >> loop but for some reason it doesn't and I can't figure out why. > >> > >> When I tried to understand why I've noticed this: > >> > >>> dif[11] > >> [1] 118.8333 > >>> linhasUpdate[10,6] > >> [1] 118.8333 > >>> dif[11]==linhasUpdate[10,6] > >> [1] FALSE > >> > >> Even though the values are the same R says they aren't! This happens for > >> some of the values (44) and for the others (128) it works fine. > >> > >> Does anybody why is this happening or a way to fix it? I' using 2.15.0. > >> > >> Thanks a lot! > >> > >> Andreia Leite > >> > >> -- > > -- > > Sarah Goslee > > http://www.functionaldiversity.org > > > > ______________________________________________ > > 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. > > > > -- > Oliver Ruebenacker, Bioinformatics and Network Analysis Consultant > President and Founder of Knowomics > (http://www.knowomics.com/wiki/Oliver_Ruebenacker) > Consultant at Predictive Medicine > (http://predmed.com/people/oliverruebenacker.html) > SBPAX: Turning Bio Knowledge into Math Models (http://www.sbpax.org) > -- Andreia Leite [[alternative HTML version deleted]] ______________________________________________ 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.
