%in% not working
Neil Klepeis <nklepeis at uclink4.berkeley.edu> writes:
I'm at a loss on this one:
> c(1.253) %in% seq(1.1,1.3,by=0.001)
[1] FALSE
> c(1.252) %in% seq(1.1,1.3,by=0.001)
[1] TRUE
> c(1.254) %in% seq(1.1,1.3,by=0.001)
[1] TRUE
"Never trust exact equality with floating point operations." Finite decimal fractions are not finite binary fractions and if you compute them in two different ways you'll very likely get differences in the last few bits because of rounding errors.
seq(1.1,1.3,by=0.001)[154]
[1] 1.253
seq(1.1,1.3,by=0.001)[154]-1.253
[1] 2.220446e-16 It's not different in principle from the fact that in 3-digit decimal arithmetic 1/3 * 3 = 0.333 * 3 = 0.999
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._