[R] Pointer to covariates?

[Thomas Lumley]

On Thu, 21 Feb 2002, Anne York wrote:

> Here is another idea, but the overhead might be just as great.
>
> dat_data.frame(y=1:3,x1=c(1,0,1),x2=c(0,1,0))
> dat.unique_unique(paste(as.character(dat$x1),as.character(dat$x2)))
> dat.keys_match(paste(as.character(dat$x1),as.character(dat$x2)),dat.unique)
>
>

The overhead should be quite small: unique() and match() both use a
hashing algorithm that should give total time and space linear in the
number of data rows (unlike the quadratic time and space needed for the
dist() solution).


	-thomas

Thomas Lumley			Asst. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

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