[R] Re : Frequency count

[Peter Dalgaard]

ssim at lic.co.nz writes:

> Dear list,
> 
> I have a dataset as follow and I would like to count the frequencies for
> the combination of the two variables (f1 and f2)  for each id. I know it is
> should be straight forward, but I just don't know how to do it in R. Here
> is the SAS code I will use to get the output I want :
> 
> proc means nway;
> class id f1 f2;
> var flag
> output out=temp;
> 
> 
> Dataset:
> id    f1    f2    flag
> 798   1     2     1
> 777   0     2     1
> 798   2     2     1
> 777   0     2     1
> 777   1     1     1
> 
> Output:
> Id=798
> 1-2   1
> 2-2   1
> 
> Id=777
> 0-2   2
> 1-1   1

Here's one way:

> dd <- read.table(stdin(),header=TRUE)
0: id    f1    f2    flag
1: 798   1     2     1
2: 777   0     2     1
3: 798   2     2     1
4: 777   0     2     1
5: 777   1     1     1
6:
> by(dd, dd$id, function(x)table(paste(x$f1,x$f2,sep="-")))
 dd$id: 777

0-2 1-1
  2   1
------------------------------------------------------------
dd$id: 798

1-2 2-2
  1   1


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907