model <- function(t, state, parms) {
  with(as.list(c(state,parms)), {
    dN1 <- N1*(b*N1/(h+N1) - d1*(1+e1*N1+c1*N2))
    dN2 <- N2*(b*N2/(h+N2) - d2*(1+e2*N2+c2*N1))
    return(list(c(dN1, dN2)))  
  }) 
}  

p <- c(b=1,c1=0.5,c2=0.5,d1=0.5,d2=0.5,e1=1,e2=1,h=0.05)
s <- c(N1=1,N2=1)
plane()