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

[Bert Gunter]

Actually, I think it's ?data.frame that he should read.

The salient points are that:
1. All data frames must have unique row names. If not provided, they
are produced. Row numbers **are** row names.

2. The return value of read methods are data frames.

-- Bert

On Mon, Jun 4, 2012 at 11:05 AM, David L Carlson <dcarlson at tamu.edu> wrote:
> 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?
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-
>> guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.



-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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