[R] vectorization question

[Liaw, Andy]

If you look at the structure, you'll see:
> x$V4 <- 0
> str(x)
`data.frame':   4 obs. of  4 variables:
 $ V1: int  1 2 3 4
 $ V2: int  5 6 7 8
 $ V3: int  9 10 11 12
 $ V4: num 0

Don't know if this is the intended result.  In any case, you're probably
better off using data.matrix, as

> data.matrix(x)
  V1 V2 V3 V4
1  1  5  9  0
2  2  6 10  0
3  3  7 11  0
4  4  8 12  0

HTH,
Andy


> -----Original Message-----
> From: Alberto Murta [mailto:amurta at ipimar.pt] 
> Sent: Thursday, August 14, 2003 12:50 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] vectorization question
> 
> 
> Dear all
> 
> I recently noticed the following error when cohercing a 
> data.frame into a 
> matrix:
> 
> > example <- matrix(1:12,4,3)
> > example <- as.data.frame(example)
> > example$V4 <- 0
> > example
>   V1 V2 V3 V4
> 1  1  5  9   0
> 2  2  6 10  0
> 3  3  7 11  0
> 4  4  8 12  0
> > example <- as.matrix(example)
> Error in as.matrix.data.frame(example) : dim<- length of dims 
> do not match the 
> length of object
> 
> However, if the column to be added has the right number of 
> lines, there's no 
> error:
> 
> > example <- matrix(1:12,4,3)
> > example <- as.data.frame(example)
> > example$V4 <- rep(0,4)
> > example
>   V1 V2 V3 V4
> 1  1  5  9  0
> 2  2  6 10  0
> 3  3  7 11  0
> 4  4  8 12  0
> > example <- as.matrix(example)
> > example
>   V1 V2 V3 V4
> 1  1  5  9  0
> 2  2  6 10  0
> 3  3  7 11  0
> 4  4  8 12  0
> 
> Shouldn't it work well both ways? I checked the attributes 
> and dims of the 
> data frame and they are the same in both cases. Where's the 
> difference that 
> originates the error message?
> Thanks in advance
> 
> Alberto
> 
> platform i686-pc-linux-gnu
> arch     i686             
> os       linux-gnu        
> system   i686, linux-gnu  
> status                    
> major    1                
> minor    7.1              
> year     2003             
> month    06               
> day      16               
> language R    
> 
> 
> -- 
>                                          Alberto G. Murta 
> Institute for Agriculture and Fisheries Research (INIAP-IPIMAR) 
> Av. Brasilia, 1449-006 Lisboa, Portugal | Phone: +351 
> 213027062 Fax:+351 213015948 | 
> http://www.ipimar-iniap.ipimar.pt/pelagicos/
> 
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list 
> https://www.stat.math.ethz.ch/mailman/listinfo> /r-help
> 

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