[R] Numeric, 2 ??? as a result of marix???

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Wolfgang Polasek
> Sent: Friday, August 28, 2009 3:16 PM
> To: r-help at r-project.org
> Subject: [R] Numeric, 2 ??? as a result of marix???
> 
> Strange things are going on in R, if you reshape a matrix in R:
> > g=gretldata[1:2,]
> > g
>    Empfang   Versand  Transit  Inland Ausland    SumS
> 1 787844.0 1307176.6 223395.4 1474726 16199.1 3809341
> 2 421473.1  306445.4 448801.2 1779402 14445.6 2970567
> > dim(g)
> [1] 2 6
> > as.vector(g)
>    Empfang   Versand  Transit  Inland Ausland    SumS
> 1 787844.0 1307176.6 223395.4 1474726 16199.1 3809341
> 2 421473.1  306445.4 448801.2 1779402 14445.6 2970567
> > gg=matrix(as.vector(g),nrow=1,byrow=TRUE)
> > gg
>      [,1]      [,2]      [,3]      [,4]      [,5]      [,6]
> [1,] Numeric,2 Numeric,2 Numeric,2 Numeric,2 Numeric,2 Numeric,2
> >

This last printout is how R prints a matrix whose contents
are a "list".  Rouughly, if a list element has length 1 its value
is printed; otherwise its type and, usually, length are printed.
E.g.,

> z<-matrix(list(one=1, two=exp(0:1), three=c("i","ii","iii"),
four=quote(log(x))), nrow=2)
> z
     [,1]      [,2]       
[1,] 1         Character,3
[2,] Numeric,2 Expression 

When you see a printout that you cannot interepret, try using the str()
function to print the object and you may be able to make sense of it.

> str(z)
List of 4
 $ : num 1
 $ : num [1:2] 1 2.72
 $ : chr [1:3] "i" "ii" "iii"
 $ : language log(x)
 - attr(*, "dim")= int [1:2] 2 2

matrix(data.frame(...)) strips the attributes from the data.frame,
making
it a list, then attaches dimensions to the list, making an object like
'z'
above.  as.matrix(data.frame()) makes a matrix that is roughly
equivalent
to the data.frame input.

Bill Dunlap
TIBCO Software Inc - Spotfire Division
wdunlap tibco.com  

>  Help please,the docu on thids is lousy!!!.
> Wolfgang
> 
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> 
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