From Andreas.Weingessel@ci.tuwien.ac.at  Fri Feb 13 14:18:26 1998
From: Andreas.Weingessel@ci.tuwien.ac.at (Andreas Weingessel)
Date: Fri, 13 Feb 1998 15:18:26 +0100
Subject: R/S differences
Message-ID: <199802131418.PAA01441@elendil.ci.tuwien.ac.at>


I noted the following R/S differences:


*) read.table behaves differently when determining the rownames. If
row.names is not given, S+ uses the first nonnumeric field with no
duplicates as the row names, whereas R uses 1:n as rownames in this case.

*) In S+ it is possible to sum over the lines of a data.frame. The
behavior of R might be more accurate in that situation, since a
data.frame is a list, but this causes problems, if one wants to use
code written for S+ in R.

S> aa<-data.frame(matrix(1:4,nrow=3D1))
S> sum(aa)
[1] 10

R> aa<-data.frame(matrix(1:4,nrow=3D1))
R> sum(aa)
Error in sum(..., na.rm =3D na.rm) : invalid argument type

*) The as.vector argument removes the vector names in S+. I do not
think that this difference can cause any problems, but I report it
just for completeness.

R> aa<-1:3
R> names(aa)<-letters[1:3]
R> as.vector(aa)
a b c=20
1 2 3=20
R> names(as.vector(aa))
[1] "a" "b" "c"

S> aa<-1:3
S> names(aa)<-letters[1:3]
S> as.vector(aa)
[1] 1 2 3
S> names(as.vector(aa))
NULL


As a final question. Does anyone know whether there is code for
nnls.fit (Linear least-squares fit with coefficients constrained to be
nonnegative.) available for R?

Thanks,
	Andreas

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*                          Andreas Weingessel                          *
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R/S differences
Andreas Weingessel