daphnids                 package:drc                 R Documentation

_D_a_p_h_n_i_a _t_e_s_t

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

     The number of immobile daphnids -in contrast to mobile daphnids-
     out of a total of 20 daphnids was counted  for several
     concentrations of a toxic substance.

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

     data(daphnids)

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

     A data frame with 16 observations on the following 4 variables.

     '_d_o_s_e' a numeric vector

     '_n_o' a numeric vector

     '_t_o_t_a_l' a numeric vector

     '_t_i_m_e' a factor with levels '24h' '48h'

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

     The same daphnids were counted at 24h and later again at 48h.

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

     Nina Cedergreen, Faculty of Life Sciences, University of
     Copenhagen, Denmark.

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

     ## Fitting a model with different parameters
     ## for different curves
     daphnids.m1 <- drm(no/total~dose, time, weights = total, 
     data = daphnids, fct = LL.2(), type = "binomial")

     ## Goodness-of-fit test
     modelFit(daphnids.m1)

     ## Summary of the data
     summary(daphnids.m1)

     ## Fitting a model with a common intercept parameter
     daphnids.m2 <- drm(no/total~dose, time, weights = total, 
     data = daphnids, fct = LL.2(), type = "binomial", 
     pmodels = list(~1, ~time))

