[R] aggregate function....

[Stephane CRUVEILLER]

Dear R users,

I have some trouble with the aggregate function. Here are my data

> daf
      S_id AF_Class count... R_gc_percent S_length
5  8264497        1       30         0.48    35678
6  8264497        3        7         0.48    35678
8  8264554        1       31         0.51    38894
9  8264554        2       11         0.51    38894
10 8264554        3        1         0.51    38894

for a given S_id, I would like to select the line corresponding to the
max count. To perform this, I used:
 > aggregate(daf,list(daf$S_id),max)
  Group.1    S_id AF_Class count... R_gc_percent S_length
1 8264497 8264497        3       30         0.48    35678
2 8264554 8264554        3       31         0.51    38894

which is ok for the count. But I realized that max function is also
applied
to AF_class (should be 1 and 1 instead of 3 and 3), so it seems that
aggregate is not the appropriate function for that I want to do. Is
there any other function I could use instead?

Best whishes,


Stéphane.
-- 
==========================================================
Stephane CRUVEILLER Ph. D.
Genoscope - Centre National de Sequencage
Atelier de Genomique Comparative
2, Rue Gaston Cremieux   CP 5706
91057 Evry Cedex - France
Phone: +33 (0)1 60 87 84 58
Fax: +33 (0)1 60 87 25 14
EMails: scruveil at genoscope.cns.fr ,scruvell at infobiogen.fr