Ratkowsky3              package:NISTnls              R Documentation

_O_n_i_o_n _g_r_o_w_t_h _d_a_t_a

_D_e_s_c_r_i_p_t_i_o_n:

     The 'Ratkowsky3' data frame has 15 rows and 2 columns.

_F_o_r_m_a_t:

     This data frame contains the following columns:

     _y A numeric vector of dry weights of onion bulbs and tops.

     _x A numeric vector of growing times.


_D_e_t_a_i_l_s:

     This model and data are an example of fitting   sigmoidal growth
     curves taken from Ratkowsky (1983).   The response variable is the
     dry weight of onion bulbs  and tops, and the predictor variable is
     growing time.

_S_o_u_r_c_e:

     Ratkowsky, D.A. (1983).   Nonlinear Regression Modeling. New York,
     NY:  Marcel Dekker, pp. 62 and 88.

_E_x_a_m_p_l_e_s:

     Try <- function(expr) if (!inherits(val <- try(expr), "try-error")) val
     plot(y ~ x, data = Ratkowsky3)

     ## causes NA/NaN/Inf error
     Try(fm1 <- nls(y ~ b1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3,
                start = c(b1 = 100, b2 = 10, b3 = 1, b4 = 1),
                trace = TRUE))
     Try(fm1a <- nls(y ~ b1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3,
                start = c(b1 = 100, b2 = 10, b3 = 1, b4 = 1),
                alg = "port", trace = TRUE))

     Try(fm2 <- nls(y ~ b1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3,
                start = c(b1 = 700, b2 = 5, b3 = 0.75, b4 = 1.3),
                trace = TRUE))
     Try(fm2a <- nls(y ~ b1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3,
                start = c(b1 = 700, b2 = 5, b3 = 0.75, b4 = 1.3),
                alg = "port", trace = TRUE))

     Try(fm3 <- nls(y ~ 1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3,
                start = c(b2 = 10, b3 = 1, b4 = 1), algorithm = "plinear",
                trace = TRUE))
     Try(fm4 <- nls(y ~ 1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3,
                start = c(b2 = 5, b3 = 0.75, b4 = 1.3), algorithm = "plinear",
                trace = TRUE))

