The _n_ construct in SAS is most analogous to that of row names in R,
accessible (and modifiable) via the row.names() function:
DF <- structure(list(Month = structure(c(2L, 2L, 2L, 2L, 1L, 1L, 1L,
1L, 3L, 3L, 3L, 3L, 3L), .Label = c("Aug", "July", "Sept"), class =
"factor"),
Week = 27:39, Estpassage = c(665L, 2232L, 9241L, 28464L,
41049L, 82216L, 230411L, 358541L, 747839L, 459682L, 609567L,
979475L, 837189L), MedFL = c(34L, 35L, 35L, 35L, 35L, 35L,
35L, 35L, 35L, 36L, 36L, 36L, 36L)), .Names = c("Month",
"Week", "Estpassage", "MedFL"), class = "data.frame", row.names = c(NA,
-13L))
DF$counter <- row.names(DF)
> DF
Month Week Estpassage MedFL counter
1 July 27 665 34 1
2 July 28 2232 35 2
3 July 29 9241 35 3
4 July 30 28464 35 4
5 Aug 31 41049 35 5
6 Aug 32 82216 35 6
7 Aug 33 230411 35 7
8 Aug 34 358541 35 8
9 Sept 35 747839 35 9
10 Sept 36 459682 36 10
11 Sept 37 609567 36 11
12 Sept 38 979475 36 12
13 Sept 39 837189 36 13
Row names, however, not guaranteed to be integer, although if not
specified at time of creation a dataframe will have its row names set
to an ascending series of integer type. Another function that would
provide similar utility for vectors might be seq_along().\, but in the
case of dataframes, it may confuse the beginning R user because it
will return a column oriented ascending sequence.
> seq_along(DF)
[1] 1 2 3 4 5
David Winsemius
On Feb 25, 2009, at 7:25 AM, Nash wrote:
>
> Have the counter function in R ?
>
> if we use the software SAS
>
> /*** SAS Code **************************/
> data tmp(drop= i);
> retain seed x 0;
> do i = 1 to 5;
> call ranuni(seed,x);
> output;
> end;
> run;
>
> data new;
> counter=_n_; ***** this keyword _n_ ****;
> set tmp;
> run;
>
> /*
> _n_ (Automatic variables)
> are created automatically by the DATA step or by DATA step statements.
> */
>
> /*** Output ********************************
> counter seed x
> 1 584043288 0.27197
> 2 935902963 0.43581
> 3 301879523 0.14057
> 4 753212598 0.35074
> 5 1607264573 0.74844
>
> ********************************************/
>
> Have a function like the "_n_" in R ?
>
>
> --
> Nash - morrison at ibms.sinica.edu.tw
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.