W1.3                   package:drc                   R Documentation

_T_h_e _t_h_r_e_e-_p_a_r_a_m_e_t_e_r _W_e_i_b_u_l_l _f_u_n_c_t_i_o_n_s

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

     'W1.3' and 'W2.3' provide the three-parameter Weibull function,
     self starter function and names of the parameters.

     'W1.3u' and 'W2.3u' provide three-parameter Weibull function where
     the upper limit is equal to 1, mainly for use with
     binomial/quantal response.

_U_s_a_g_e:

       W1.3(fixed = c(NA, NA, NA), names = c("b", "d", "e"), ...)
       
       W2.3(fixed = c(NA, NA, NA), names = c("b", "d", "e"), ...)
       
       W1.3u(upper = 1, fixed = c(NA, NA, NA), names = c("b", "c", "e"), ...)  
       
       W2.3u(upper = 1, fixed = c(NA, NA, NA), names = c("b", "c", "e"), ...)    

_A_r_g_u_m_e_n_t_s:

   upper: numeric value. The fixed, upper limit in the model. Default
          is 1.

   fixed: numeric vector. Specifies which parameters are fixed and at
          what value they are fixed.  NAs for parameter that are not
          fixed.

   names: a vector of character strings giving the names of the
          parameters. The default is reasonable.

     ...: additional arguments to be passed from the convenience
          functions.

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

     The three-parameter Weibull model is given by the expression

               f(x) = 0 + (d-0)exp(-exp(b(log(x)-e))).


     The function is asymmetric about the inflection point, that is the
     parameter exp(e).

     The three-parameter Weibull model with upper limit 1 is given by
     the expression

               f(x) = 0 + (1-0)exp(-exp(b(log(x)-e))).

_V_a_l_u_e:

     See 'weibull1'.

_N_o_t_e:

     This function is for use with the function 'drm'.

_A_u_t_h_o_r(_s):

     Christian Ritz

_S_e_e _A_l_s_o:

     Related functions are 'W1.4' and 'weibull1'.

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

     ## Fitting a three-parameter Weibull model
     ryegrass.m1 <- drm(rootl ~ conc, data = ryegrass, fct = W1.3())
     ryegrass.m1

