On Thu, 2006-10-05 at 03:10 +0200, [EMAIL PROTECTED] wrote: > Full_Name: Brad Christoffersen > Version: 2.3.1 > OS: Windows XP > Submission from: (NULL) (128.196.193.132) > > > Why is the difference between two numbers so different from the "mean relative > difference" output from the all.equal() function? Is this an artifact of the > way R stores numerics? I could not find this problem as I searched through > the > submitted bugs. But I am brand new to R so I apologize if there is something > obvious I'm missing here. > > rm(list=ls(all=TRUE)) ## Remove all objects that could hinder w/ consistent > output > a <- 204 > b <- 203.9792 > all.equal(a,b) > [1] "Mean relative difference: 0.0001019608" > a - b > [1] 0.0208
Read the Details section of ?all.equal, which states: Numerical comparisons for scale = NULL (the default) are done by first computing the mean absolute difference of the two numerical vectors. If this is smaller than tolerance or not finite, absolute differences are used, otherwise relative differences scaled by the mean absolute difference. If scale is positive, absolute comparisons are made after scaling (dividing) by scale Thus on R version 2.4.0 (2006-10-03): > all.equal(a, b, scale = 1) [1] "Mean scaled difference: 0.0208" Please do not report doubts about behavior as bugs. Simply post a query on r-help first. If it is a bug, somebody will confirm it and you can then report it as such. BTW, time to upgrade...Go Wildcats! HTH, Marc Schwartz ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
