maysingle = function(r,k,noise, n0,nostep){
#calculates one time series of the May's equation 

#r - growth rate
#k - carrying capacity
#n0 - initial population size
#nostep - number of steps for simulation
#noise - absolute noise 

  n = rep(NA,nostep+1)
  n[1] = n0
  for (t in 1:nostep) {
     nprime = r*n[t]*(k-n[t])/k + rnorm(1,0,noise)*n[t]
     if (nprime < 0)
        nprime = 0;
     n[t+1] = nprime
  }
  n
}