Dear Titus,
Your first function can be simplified to
splice <- function(x, y) {
as.vector(rbind(x, y))
}
For factors, you better convert them first back to character strings.
splice <- function(x, y) {
x <- levels(x)[x]
y <- levels(y)[y]
factor(as.vector(rbind(x, y)))
}
HTH,
Thierry
------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
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tel. + 32 54/436 185
thierry.onkel...@inbo.be
www.inbo.be
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than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher
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ensure that a reasonable answer can be extracted from a given body of
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-----Oorspronkelijk bericht-----
Van: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
Namens Titus von der Malsburg
Verzonden: dinsdag 9 juni 2009 11:12
Aan: r-help@r-project.org
Onderwerp: [R] Splicing factors without losing levels
Hi list!
An operation that I often need is splicing two vectors:
> splice(1:3, 4:6)
[1] 1 4 2 5 3 6
For numeric vectors I use this hack:
splice <- function(x, y) {
xy <- cbind(x, y)
xy <- t(xy)
dim(xy) <- length(x) * 2
return(xy)
}
So far, so good (?). But I also need splicing for factors and I tried
this:
splice <- function(x, y) {
xy <- cbind(x, y)
xy <- t(xy)
dim(xy) <- length(x) * 2
if (is.factor(x) && is.factor(y)) {
xy <- as.factor(xy)
levels(xy) <- levels(x)
}
return(xy)
}
This, however, doesn't work because the level name to integer mapping
gets mixed up when copying the levels from x to xy.
My questions:
1.) How can this be fixed?
2.) What's the best way to do splicing of vectors and factors in R?
(I couldn't find a prefdefined function for this although it seems to
be such a basic and useful operation.)
Thanks!!
Titus
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