[Rd] as.data.frame.matrix() returns an invalid object

[Bert Gunter]

... and further

> identical(as.list(df2),as.list(df1))
[1] TRUE

in R 2.15.0

Not sure whether these sorts of degenerate cases are of much value,
though. But I'll leave that for the wizards.

-- Bert

On Wed, Oct 10, 2012 at 11:22 PM, Hervé Pagès <hpages at fhcrc.org> wrote:
> Hi,
>
> Two ways to create what should normally be the same data frame:
>
>   > df1 <- data.frame(a=character(0), b=character(0))> df1
>   [1] a b
>   <0 rows> (or 0-length row.names)
>
>   > df2 <- as.data.frame(matrix(character(0), ncol=2, dimnames=list(NULL,
> letters[1:2])))
>   > df2
>   [1] a b
>   <0 rows> (or 0-length row.names)
>
> unique() works as expected except that I get a warning on 'df2':
>
>   > unique(df1)
>   [1] a b
>   <0 rows> (or 0-length row.names)
>
>   > unique(df2)
>   [1] a b
>   <0 rows> (or 0-length row.names)
>   Warning message:
>   In is.na(rows) : is.na() applied to non-(list or vector) of type 'NULL'
>
> Look like the two data frames are not identical:
>
>   > identical(df1, df2)
>   [1] FALSE
>
>   > all.equal(df1, df2)
>   [1] "Attributes: < Length mismatch: comparison on first 1 components >"
>
>   > attributes(df1)
>   $names
>   [1] "a" "b"
>
>   $row.names
>   integer(0)
>
>   $class
>   [1] "data.frame"
>
>   > attributes(df2)
>   $names
>   [1] "a" "b"
>
>   $class
>   [1] "data.frame"
>
> Actually 'df2' is considered broken by validObject():
>
>   > validObject(df1)
>   [1] TRUE
>
>   > validObject(df2)
>   Error in validObject(df2) :
>     invalid class “data.frame” object: slots in class definition but not in
> object: "row.names"
>
> This is with R 2.15 and recent R devel.
>
> Cheers,
> H.
>
> --
> Hervé Pagès
>
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N, M1-B514
> P.O. Box 19024
> Seattle, WA 98109-1024
>
> E-mail: hpages at fhcrc.org
> Phone:  (206) 667-5791
> Fax:    (206) 667-1319
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel



-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm