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

On 8/31/07, Peter Dalgaard <P.Dalgaard@biostat.ku.dk> 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
> ~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45)
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>
>
>

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