[R] tapply on a matrix?

[Thomas Lumley]

On Fri, 20 Apr 2001, Jon McAuliffe wrote:

>
> suppose i have an nx2 matrix A; call its column vectors
> x and y. the rows of A are grouped by a factor F. i want to fit
> one lowess curve (y vs. x) for each subset of rows corresponding
> to a particular level of F. naively, i mean something like
>
> tapply(A, F, fun = lowess)  ,
>
> but tapply needs A to be 1-dimensional. reading the help pages,
> the other {,l,s}apply functions seem not to be germane in this
> situation either. what's the correct approach here?

by()

	-thomas

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

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