Yes, floating point issue. See e.g.
http://cran.r-project.org/doc/FAQ/R-FAQ.html 7.31 Why doesn't R think these numbers are equal? > options(digits = 22) > 29/50 [1] 0.579999999999999960032 > 29/50 * 50 [1] 28.99999999999999644729 > 29*50/50 [1] 29.00000000000000000000 > .58 * 50 [1] 28.99999999999999644729 > floor(28.999999) [1] 28.00000000000000000000 > floor(29.000000) [1] 29.00000000000000000000 > Steven McKinney Statistician Molecular Oncology and Breast Cancer Program British Columbia Cancer Research Centre > -----Original Message----- > From: bioc-devel-boun...@r-project.org [mailto:bioc-devel-bounces@r- > project.org] On Behalf Of Ou, Jianhong > Sent: December-19-13 1:53 PM > To: bioc-devel@r-project.org > Subject: [Bioc-devel] simple question about floor > > Hi all, > > Maybe this is not a bioconductor question but R. However, I feel this is > very interesting. > > I tried > > > floor(29/50*50) > [1] 28 > > floor(29*50/50) > [1] 29 > > Is this a floating-point problem? How could we explain this? > > Yours sincerely, > > Jianhong Ou > > LRB 670A > Program in Gene Function and Expression > 364 Plantation Street Worcester, > MA 01605 > > [[alternative HTML version deleted]] > > _______________________________________________ > Bioc-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/bioc-devel _______________________________________________ Bioc-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/bioc-devel
