[R] index after rbind

[John Fox]

Dear Ann,

To elaborate Spencer's answer slightly, R requires that the row names of a 
data frame be unique. That's why it generated different row names for the 
rows of the two data frames given as arguments to rbind.

Again, the question is what you want to do here. You could generate more 
meaningful row names (e.g., "A1" - "A5", "B1" - "B5" for your original 
example) if this seems appropriate, but they have to be unique.

John

At 09:34 AM 4/21/2003 -0700, Spencer Graves wrote:
> > df1 <- data.frame(a=1:2)
> > df2 <- rbind(df1, df1)
> > df2
>    a
>1  1
>2  2
>11 1
>22 2
> > rownames(df2) <- 1:4
>
>hope this helps. spencer graves
>
>Ann Hess wrote:
>>I am using rbind to concatenate two dataframes, but after the rbind I get
>>a strange "double" index.
>>I am using rbind a number of times to make one large dataset.  Is there a
>>way to prevent the "double" index?  Or is there some other way to
>>concatenate the data (it looks like merge only works by columns)?
>>Here is an example of the "double" index.
>>
>>>numbers<-(1:5)
>>>letters<-matrix(c("a","b","c","d","e"),5,1)
>>>data<-data.frame(letters,numbers)
>>>doubledata<-rbind(data,data)
>>>doubledata
>>    letters numbers
>>1        a       1
>>2        b       2
>>3        c       3
>>4        d       4
>>5        e       5
>>11       a       1
>>22       b       2
>>33       c       3
>>44       d       4
>>55       e       5
>>______________________________________________
>>R-help at stat.math.ethz.ch mailing list
>>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>
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____________________________
John Fox
Department of Sociology
McMaster University
email: jfox at mcmaster.ca
web: http://www.socsci.mcmaster.ca/jfox