Andrew Yee wrote: > Thanks for the clarification. I should have recognized the difference > between "warning" and "error." > But if I may take this a step further, shouldn't it then be exact=TRUE > instead of exact=NULL? > Thanks, > Andrew >
Nope. The two are equivalent for the Spearman test, but not for Kendall's tau. The login in that case is that NULL implies exact testing if n < 50 and asymptotic otherwise. TRUE and FALSE enforces one or the other (if possible). > On 8/31/07, Peter Dalgaard <[EMAIL PROTECTED]> wrote: > >> Andrew Yee wrote: >> >>> Pardon my ignorance, but is there a difference in cor.test between >>> exact=FALSE and exact=NULL when method=spearman? >>> >>> Take for example: >>> >>> x<-c(1,2,2,3,4,5) >>> y<-c(1,2,2,10,11,12) >>> cor.test(x,y, method="spearman", exact=NULL) >>> >>> This gives an error message, >>> Warning message: Cannot compute exact p-values with ties in: >>> cor.test.default(x, y, method = "spearman", exact = NULL) >>> >>> However, when exact is changed to FALSE, this seems to run okay. >>> >>> cor.test(x,y, method="spearman", exact=FALSE) >>> >>> Question: should this be exact = FALSE in the documentation and/or the >>> >> code? >> >>> >> No. The default is indeed NULL. >> >> This implies that calculation of exact p-values will be attempted, and >> when there are ties you get a warning (NB: not error) message. Setting >> exact=FALSE, no attempt is made and no warning is given. >> >>> Thanks, >>> Andrew >>> MGH Cancer Center >>> >>> ______________________________________________ >>> R-help@stat.math.ethz.ch 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. >>> >>> >> >> -- >> O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B >> c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K >> (*) \(*) -- University of Copenhagen Denmark Ph: (+45) >> 35327918 >> ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) >> 35327907 >> >> >> >> > > [[alternative HTML version deleted]] > > > ------------------------------------------------------------------------ > > ______________________________________________ > R-help@stat.math.ethz.ch 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. > -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ R-help@stat.math.ethz.ch 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.
