nl<- nls(formula = water ~ cbind(1,poly(time,4),sin(omega_1*time+phi_1),
                        sin(omega_2*time+phi_2),
                        sin(omega_3*time+phi_3)), data = fhw,
          start = list(omega_1=(2*pi)/545,omega_2=(2*pi)/205,omega_3=(2*pi)/85,phi_1=pi,phi_2=pi,phi_3=pi),
          algorithm = "plinear",control = list(maxiter = 1000))