[R] vectorization question

[Alberto Murta]

Thank you very much. I just would expect that 'as.matrix' would have the same 
behaviour as 'data.matrix' when all columns in a data frame are numeric.
Regards

Alberto

On Thursday 14 August 2003 16:41, Liaw, Andy wrote:
> 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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-- 
                                         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/