[R] constrained sample

[Rogério Rosa da Silva]

Dear List,

Is there an way to do a randomization (with sample) on a column and that 
maintain fixed the occurrence totals (i.e, numbers different of zeros) on a 
factor column ?

Thanks in advance

-- 
Rogério R. Silva
MZUSP http://www.mz.usp.br
Linux User #354364
Linux counter http://counter.li.org

# description file:
factors	occurrence
A	1
A	7
A	5
A	0
B	1
B	5
B	0
B	0
C	3
C	4
C	5
C	0
D	0
D	0
D	0
D	1