[R] randomize a matrix

[Guenther, Cameron]

Hello everyone,

If I have an incidence matrix of 0 and 1's 

P=[1 1 1 1 1 1
   1 1 1 1 0 0 
   1 1 1 0 0 0
   1 1 1 0 0 0
   1 1 0 0 0 0]

I want to create a new uniform random matrix [a] that is filled with 0's
and 1's but constrained so that the row and column sums are the same as
in [P].  Does anyone know how to accomplish this?

Thanks in advance  

Cameron Guenther, Ph.D. 
Associate Research Scientist
FWC/FWRI, Marine Fisheries Research
100 8th Avenue S.E.
St. Petersburg, FL 33701
(727)896-8626 Ext. 4305
cameron.guenther at myfwc.com