[R] A More efficient method?

[ONKELINX, Thierry]

Cat <- c('a','a','a','b','b','b','a','a','b')
C1 <- ifelse(Cat == 'a', -1, 1)

------------------------------------------------------------------------
----
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
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx op inbo.be
www.inbo.be 

Do not put your faith in what statistics say until you have carefully
considered what they do not say.  ~William W. Watt
A statistical analysis, properly conducted, is a delicate dissection of
uncertainties, a surgery of suppositions. ~M.J.Moroney

 

> -----Oorspronkelijk bericht-----
> Van: r-help-bounces op stat.math.ethz.ch 
> [mailto:r-help-bounces op stat.math.ethz.ch] Namens Keith Alan 
> Chamberlain
> Verzonden: woensdag 4 juli 2007 15:45
> Aan: r-help op stat.math.ethz.ch
> Onderwerp: [R] A More efficient method?
> 
> Dear Rhelpers,
> 
> Is there a faster way than below to set a vector based on 
> values from another vector? I'd like to call a pre-existing 
> function for this, but one which can also handle an 
> arbitrarily large number of categories. Any ideas?
> 
> Cat=c('a','a','a','b','b','b','a','a','b')	# Categorical variable
> C1=vector(length=length(Cat))	# New vector for numeric values
> 
> # Cycle through each column and set C1 to corresponding value of Cat.
> for(i in 1:length(C1)){
> 	if(Cat[i]=='a') C1[i]=-1 else C1[i]=1
> }
> 
> C1
> [1] -1 -1 -1  1  1  1 -1 -1  1
> Cat
> [1] "a" "a" "a" "b" "b" "b" "a" "a" "b"
> 
> Sincerely,
> KeithC.
> Psych Undergrad, CU Boulder (US)
> RE McNair Scholar
> 
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