FAQ 7.31: Why doesn't R think these numbers are equal? http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f
b On Wed, Mar 31, 2010 at 10:10 AM, Gianluca Baio <gianl...@statistica.it> wrote: > Dear list, > I have observed a weird behaviour from R --- apologies if I am missing > something obvious! > > df3f826f28 > df3f826f28 > Say you type in R: > >>c.preec <- 10074 >>c.gd <- 2200 >>p1 <- .2 >>c.neo <- p1*9451 + (1-p1)*3883 >>n.preec <- 3710 >>n.gd <- 2650 >>n.neo <- 2120 >>n.pcos <- 53000 >>unit.met <- 94 >>cost.met <- 94*n.pcos > >>effect <- seq(0,1,.01) >>gross.save <- ((n.preec*effect*c.preec) + (n.gd*effect*c.gd) + > (n.neo*effect*c.neo)) >>save.nhs <- gross.save - cost.met > >>e.star <- .4 >>s.star <- save.nhs[which(effect==e.star)]/1000000 > > Now, R should return >> which(effect==e.star) = 41 > > and therefore compute the variable s.star. > All well and trivial; but if you try and set >>e.star <- .7 > > R returns >>which(effect==e.star) = integer(0) > > so apparently there is no element in the vector e.star that is equal to .7. > Of course, there should be, since effect <- seq(0,1,.01), and in fact if you > ask R to show you the vector effect, you do get > [1] 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 > 0.14 > [16] 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 > 0.29 > [31] 0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 > 0.44 > [46] 0.45 0.46 0.47 0.48 0.49 0.50 0.51 0.52 0.53 0.54 0.55 0.56 0.57 0.58 > 0.59 > [61] 0.60 0.61 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 *0.70* 0.71 0.72 0.73 > 0.74 > [76] 0.75 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 > 0.89 > [91] 0.90 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1.00 > > Can anyone think of why this happens? > Many thanks > Gianluca > > [[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. > ______________________________________________ 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.
