# dist(*, "euclidean") [was "dist function suggestion"]

**Prof Brian Ripley
**
Prof Brian Ripley <ripley@stats.ox.ac.uk>

*Wed, 20 Jan 1999 13:48:53 +0000 (GMT)*

>* BDR> You will need to call it something else: dist is a clone of an S
*>* BDR> function, and dist(X, "manhattan") is well-established usage.
*>*
*>* one could still imagine an extra Y argument such that
*>* dist(X, Y=myY, method="euclidean")
*>* and dist(X, "euclidean", Y=myY)
*>* would work
*>* one could even make it such that
*>* both
*>* dist(X, myY)
*>* and dist(X, "euclidean")
*>* would work. However, the extra hack for dist(X, Y)
*
Um, I did think about that, but precisely what would be rules be?
For now the second argument can be anything coercable to a character
(why is match.arg not used?), or should be since ?pmatch says
x: the values to be matched.
without mentioning mode, although the internal code has isString
(whatever precisely that is). In particular, names fail in R but not
S, although as documented they should work in R but not S:
>* pmatch(as.name("test"), "test")
*Error in pmatch(x, table, duplicates.ok) : argument is not of mode character
So at present if the second argument is a character matrix it works.
And there is an as.matrix on X. So what do you want Y to be?
numeric? (At present I can have X as a data frame with factors, e.g.
dist(data.frame(factor(1:10)))!) matrix? ?
While I am at it
>* X <- c(Inf, 0, 0)
*>* library(mva)
*>* dist(X)
*Error: NAs in foreign function call (arg 1)
is confusing: the error message is caused by Infs too. (I found this
when writing a version of dist to handle NAs as S's does: the bare code is
now an example in the V&R R complements.)
Brian
--
Brian D. Ripley, ripley@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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