[R] Why do I have a column called row.names?

[David L Carlson]

Try help("read.delim") - always a good strategy before using a function for
the first time:

In it, you will find: "Using row.names = NULL forces row numbering. Missing
or NULL row.names generate row names that are considered to be 'automatic'
(and not preserved by as.matrix)."

----------------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77843-4352


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Ed Siefker
> Sent: Monday, June 04, 2012 12:47 PM
> To: r-help at r-project.org
> Subject: [R] Why do I have a column called row.names?
> 
> I'm trying to read in a tab separated table with read.delim().
> I don't particularly care what the row names are.
> My data file looks like this:
> 
> 
> start   stop    Symbol  Insert sequence Clone End Pair  FISH
> 203048  67173930        ABC8-43024000D23                TI:993812543
>  TI:993834585
> 255176  87869359        ABC8-43034700N15                TI:995224581
>  TI:995237913
> 1022033 1060472 ABC27-1253C21           TI:2094436044   TI:2094696079
> 1022033 1061172 ABC23-1388A1            TI:2120730727   TI:2121592459
> 
> 
> 
> I have to do something with row.names because my first column has
> duplicate entries.  So I read in the file like this:
> 
> > BACS<-read.delim("testdata.txt", row.names=NULL, fill=TRUE)
> > head(BACS)
>   row.names    start             stop Symbol Insert.sequence
> Clone.End.Pair
> 1    203048 67173930 ABC8-43024000D23     NA    TI:993812543
> TI:993834585
> 2    255176 87869359 ABC8-43034700N15     NA    TI:995224581
> TI:995237913
> 3   1022033  1060472    ABC27-1253C21     NA   TI:2094436044
> TI:2094696079
> 4   1022033  1061172     ABC23-1388A1     NA   TI:2120730727
> TI:2121592459
>   FISH
> 1   NA
> 2   NA
> 3   NA
> 4   NA
> 
> 
> Why is there a column named "row.names"?  I've tried a few different
> ways of invoking this, but I always get the first column named
> row.names,
> and the rest of the columns shifted by one.
> 
> Obviously I could fix this by using row.names<-, but I'd like to
> understand
> why this happens.  Any insight?
> 
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