Simple rules yield complex food webs (2000)Richard J. Williams & Neo D. MartinezNiche Model

Niche_Model_WM

### Niche-Food Web Model - Williams et Martinez
 
#### Parameters
 
# S = Number of trophic species
# C = Network connectance [0,0.5[
 
 
nicheFW <- function(S,C){
### Model
vec_n <- runif(S)
vec_r <- rbeta(S,1,1/(2*C)-1)*vec_n
vec_c <- runif(S,vec_r/2,vec_n)
vec_r_inf <- vec_c - vec_r/2
vec_r_sup <- vec_c + vec_r/2
 
out <- matrix(0, nrow=S,ncol=S)
 
for (y in 1:S){
  for (i in y:S){
      if(vec_n[y]>=vec_r_inf[i] & vec_n[y]<=vec_r_sup[i]) out[i,y]=1
      if(vec_n[i]>=vec_r_inf[y] & vec_n[i]<=vec_r_sup[y]) out[y,i]=1
    }
  }
  return(out)
}
 
Co = function(x) sum(x)/prod(dim(x))
 
REPL = replicate(200, Co(nicheFW(80, 0.1)))
plot(density(REPL))
summary(REPL)