wtloss package:MASS R Documentation _W_e_i_g_h_t _L_o_s_s _D_a_t_a _f_r_o_m _a_n _O_b_e_s_e _P_a_t_i_e_n_t _D_e_s_c_r_i_p_t_i_o_n: The data frame gives the weight, in kilograms, of an obese patient at 52 time points over an 8 month period of a weight rehabilitation programme. _U_s_a_g_e: wtloss _F_o_r_m_a_t: This data frame contains the following columns: '_D_a_y_s' time in days since the start of the programme. '_W_e_i_g_h_t' weight in kilograms of the patient. _S_o_u_r_c_e: Dr T. Davies, Adelaide. _R_e_f_e_r_e_n_c_e_s: Venables, W. N. and Ripley, B. D. (2002) _Modern Applied Statistics with S._ Fourth edition. Springer. _E_x_a_m_p_l_e_s: wtloss.fm <- nls(Weight ~ b0 + b1*2^(-Days/th), data = wtloss, start = list(b0=90, b1=95, th=120), trace = TRUE)