[R] Request for help

[Michela Marignani]

My name is Michela Marignani and I'm an ecologist trying to solve a problem 
linked to knight' s tour algorithm.
I need a program to create random matrices with presence/absence (i.e. 1,0 
values), with defined colums and rows sums, to create null models for 
statistical comparison of species distribution phenomena.
I've seen on the web many solutions of the problem, but none provides the 
freedom to easily change row+colums constraint and none of them produce 
matrices  with 1 and 0. Also, I've tryied to use R, but it is too 
complicated for a not-statistician as I am....can you help me?

Thank you for your attention,
so long

Michela Marignani
University of Siena
Environmental Science Dept.
Siena, Italy
michela.marignani at uniroma1.it