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

Hervé Pagès hpages at fhcrc.org
Thu Oct 11 08:22:55 CEST 2012


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)
   [1] "a" "b"


   [1] "data.frame"

   > attributes(df2)
   [1] "a" "b"

   [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.


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

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