[R] Cutting vectors

[Ben Bolker]

  Without being sure, I think what you're trying to do is achieved by
match().

 Example:

> x <- factor(1:4)
> y <- c(7,5,3,8)
> z <- c(2,3,1)
> y[z==x]
numeric(0)
Warning messages: 
1: longer object length
	is not a multiple of shorter object length in: is.na(e1) | is.na(e2) 
2: longer object length
	is not a multiple of shorter object length in: ==.default(z, x) 
> y[match(z,x)]
[1] 5 3 7

  Question: what cross-references in the documentation would have helped
you find this?  What keywords would you have looked for?
  I'm vaguely thinking about putting together a list of "How do I ... in
R?"

  Ben

On Sun, 2 Apr 2000, Patrik Waldmann wrote:

> 
> > Patrik Waldmann wrote: > > > I have one factor with say five levels
> (fact) of different size and a corresponding variable (var). I
> randomly generate five new levels (nfact ex. 2,2,1,5,4). What I would
> like to do is to extract the corresponding variable values into a new
> variable (nvar). I did try the following, why doesn't it work?  
> nvar<-var[fact==nfact[ ]] > > ..I ain't sure I get evrything but try >
> > > nvar<-var[which(fact == nfact)] >
> 
> Gives me the same error message as before (and creates a meaningless vector): 
> 
> Warning messages: 
> 1: longer object length
>         is not a multiple of shorter object length in: is.na(e1) | is.na(e2) 
> 2: longer object length
>         is not a multiple of shorter object length in: ==.default(fact, nfact)
> 
> Has this something to with the non-equal size of the 'cuttings'?
> 
> Patrik
> 
> 
> 
> 
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-- 
Ben Bolker                                  bolker at zoo.ufl.edu
Zoology Department, University of Florida   http://www.zoo.ufl.edu/bolker
318 Carr Hall/Box 118525                    tel: (352) 392-5697
Gainesville, FL 32611-8525                  fax: (352) 392-3704

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