[R] Data frame question

[Claudia Beleites]

Andy,

Did you run into any kind of trouble?
I'm asking because I'm maintaining a package for spectroscopic data that heavily 
uses "I (spectra.matrix)" ...

However, once you have the matrix safe inside the data.frame, you can delete the 
  "AsIs":

 > a <- matrix (1:9, 3)
 > str (a)
  int [1:3, 1:3] 1 2 3 4 5 6 7 8 9
 > df <- data.frame (a = I (a))
 > str (df)
'data.frame':	3 obs. of  1 variable:
  $ a: 'AsIs' int [1:3, 1:3] 1 2 3 4 5 6 7 8 9
 > df$a <- unclass (df$a)
 > str (df)
'data.frame':	3 obs. of  1 variable:
  $ a: int [1:3, 1:3] 1 2 3 4 5 6 7 8 9
 > df$a
      [,1] [,2] [,3]
[1,]    1    4    7
[2,]    2    5    8
[3,]    3    6    9
 > dim (df)
[1] 3 1

However, I don't know whether something can now trigger a conversion to 
data.frame that the AsIs would have stopped.

Cheers,

Claudia

apjaworski at mmm.com wrote:
> Hi,
> 
> I have the following question about creating data frames.  I want to 
> create a data frame with 2 components: a vector and a matrix.
> 
> Let me use a simple example:
> 
> y <- rnorm(10)
> x <- matrix(rnorm(150), nrow=10)
> 
> Now if I do
> 
> dd <- data.frame(x=x, y=y)
> 
> I get a data frame with 16 colums, but if, according to the documentation, 
>  I do
> 
> dd <- data.frame(x=I(x), y=y)
> 
> then str(dd) gives:
> 
> 'data.frame':   10 obs. of  2 variables:
>  $ x: AsIs [1:10, 1:15] 0.700073.... -0.44371.... -0.46625.... 
> 0.977337.... 0.509786.... ...
>  $ y: num  0.4676 -1.4343 -0.3671 0.0637 -0.231 ...
> 
> This looks and works OK.
> 
> Now, there exists a CRAN package called pls.  It has a yarn data set in 
> it.
> 
>> data(yarn)
>> str(yarn)
> 'data.frame':   28 obs. of  3 variables:
>  $ NIR    : num [1:28, 1:268] 3.07 3.07 3.08 3.08 3.1 ...
>   ..- attr(*, "dimnames")=List of 2
>   .. ..$ : NULL
>   .. ..$ : NULL
>  $ density: num  100 80.2 79.5 60.8 60 ...
>  $ train  : logi  TRUE TRUE TRUE TRUE TRUE TRUE ...
> 
> This looks almost the same, except the matrix component in my example has 
> the AsIs instead of num.
> 
> Is this just some older behavior of the data.frame function producing this 
> difference?  If not, how can I get my data frame (dd) to look like yarn?
> 
> I read the help pages for data.frame and as.data.frame and found this 
> paragraph
> 
> If a list is supplied, each element is converted to a column in the data 
> frame. Similarly, each column of a matrix is converted separately. This 
> can be overridden if the object has a class which has a method for 
> as.data.frame: two examples are matrices of class "model.matrix" (which 
> are included as a single column) and list objects of class "POSIXlt" which 
> are coerced to class "POSIXct". 
> 
> If I do 
> 
>> methods(as.data.frame)
>  [1] as.data.frame.aovproj*        as.data.frame.array 
>  [3] as.data.frame.AsIs            as.data.frame.character 
>  [5] as.data.frame.complex         as.data.frame.data.frame 
>  [7] as.data.frame.Date            as.data.frame.default 
>  [9] as.data.frame.difftime        as.data.frame.factor 
> [11] as.data.frame.ftable*         as.data.frame.integer 
> [13] as.data.frame.list            as.data.frame.logical 
> [15] as.data.frame.logLik*         as.data.frame.matrix 
> [17] as.data.frame.model.matrix    as.data.frame.numeric 
> [19] as.data.frame.numeric_version as.data.frame.ordered 
> [21] as.data.frame.POSIXct         as.data.frame.POSIXlt 
> [23] as.data.frame.raw             as.data.frame.table 
> [25] as.data.frame.ts              as.data.frame.vector 
> 
> so it looks like there is a matrix method for as.data.frame.  The question 
> then is how can I override the default behavior for the matrix object 
> (converting columns separately).
> 
> 
> Any hint will be appreciated,
> 
> Andy
> 
> 
> __________________________________
> Andy Jaworski
> 518-1-01
> Process Laboratory
> 3M Corporate Research Laboratory
> -----
> E-mail: apjaworski at mmm.com
> Tel:  (651) 733-6092
> Fax:  (651) 736-3122
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> 
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-- 
Claudia Beleites
Dipartimento dei Materiali e delle Risorse Naturali
Università degli Studi di Trieste
Via Alfonso Valerio 6/a
I-34127 Trieste

phone: +39 0 40 5 58-37 68
email: cbeleites at units.it