Generates a random bipartite web, based on r2dtable
and lognormal marginal distributions.
1  genweb(N1 = 10, N2 = 30, dens = 2)

N1 
Number of species in the lower trophic level; or a vector of length 2 giving number of lower and higher trophic level species. Defaults to 10. Large values (>70) will take much longer! 
N2 
Number of species in the higher trophic level. Ignored if N1 a vector of length 2. Defaults to 30. Large values (>70) will take much longer! 
dens 
Interaction density, i.e. how many interactions there shall be, on average, for each link. Defaults to 2 (the median observed interaction density in the NCEAS pollination webs). Large values (> 10) will take much longer to find matrices for. 
This function can be used to create simple, but not necessarily realistic, bipartite webs for given dimensionality and interaction density. Marginal distributions are assumed to be lognormal, mean and standard deviation are calculated from N1, N2 and dens (see code for details).
A matrix with N1 x N2 species.
Can be a bit timeconsuming for large webs, because the absolute values for both dimensions have to match perfectly. This involves a rather inelegant while
loop.
Jochen Fründ and Carsten F. Dormann
1  genweb()

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