[R] how to combine multiple indicator variables in a single factor

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Daniel Nordlund
> Sent: Friday, December 18, 2009 12:49 PM
> To: r-help at r-project.org
> Subject: [R] how to combine multiple indicator variables in a 
> single factor
> 
> Say I have a dataframe like this:
> 
> df <- data.frame(cbind(c(1,0,0,1),c(0,1,0,0),c(0,0,1,0)))
> 
> names(df) <- c('a','b','c')
> 
> I would like to create a factor in a new column, where the 
> factor values are taken from the column names, like this:
> 
> > df2
>   a b c f
> 1 1 0 0 a
> 2 0 1 0 b
> 3 0 0 1 c
> 4 1 0 0 a
> 
> How would I do this?  Thanks,

One possibility is
   > df$f <- factor(df$a + df$b*2 + df$c*3, labels=names(df)[1:3])
   > df
     a b c f
   1 1 0 0 a
   2 0 1 0 b
   3 0 0 1 c
   4 1 0 0 a


Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> 
> Dan
> 
> Daniel Nordlund
> Bothell, WA USA
> 
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