[R] Need advise in grab the line number of sorted list in R

[Marc Schwartz]

on 06/02/2008 08:45 AM Jason Lee wrote:
> Hi,
> 
> I have a data frame which format is like below:-
> 
>         X     Y     Z
> 131 22.2 3.4   4.4
> 150  20.0 12.2 4.5
> 
> etc...
> 
> And I have sorted the data frame. However, I would like to grab one of these
> elements in the data frame. Also, i would like to number these rows so that
> when i grab a particular line let say 150, it is able to return me the
> position of the row rather than the "150". Let say in this example, when i
> grab a value of 150, it gives me 2 rather than 150.
> 
> 
> I tried to add anohter extra column of number which is  data$NUMBER =
> row.names(data) on the sorted data but it seems not giving what I wanted
> which is the "position" of the row 150.
> 
> Please advise. Thanks.

Is this what you want?

 > DF
        X    Y   Z
131 22.2  3.4 4.4
150 20.0 12.2 4.5


 > which(row.names(DF) == 150)
[1] 2


See ?which

HTH,

Marc Schwartz