[R] (no subject)

[David Winsemius]

On Jan 25, 2010, at 1:46 PM, Chuck White wrote:

> Hello -- I would like to know of a more efficient way of writing the  
> following piece of code. Thanks.
>
> options(stringsAsFactors=FALSE)
> orig <- c(rep('11111111',100000),rep('22222222', 
> 200000),rep('33333333',300000),rep('44444444',400000))
> orig.unique <- unique(orig)
> system.time(df <- as.data.frame(sapply(orig.unique, function(x)  
> ifelse(orig==x, 1, 0))))

 > system.time(df <- model.matrix(~orig))
    user  system elapsed
   3.122   0.204   3.312
Warning message:
In model.matrix.default(~orig) : variable 'orig' converted to a factor
 >
 > options(stringsAsFactors=FALSE)
 > orig <- c(rep('11111111',100000),rep('22222222', 
200000),rep('33333333',300000),rep('44444444',400000))
 > orig.unique <- unique(orig)
 > system.time(df <- as.data.frame(sapply(orig.unique, function(x)  
ifelse(orig==x, 1, 0))))
    user  system elapsed
  18.455   0.872  19.234


>
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