compParm                 package:drc                 R Documentation

_C_o_m_p_a_r_i_s_o_n _o_f _p_a_r_a_m_e_t_e_r_s

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

     Compare parameters from different assays, either by means of
     ratios or differences.

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

     compParm(object, strVal, operator = "/", od = FALSE, pool = TRUE, display = TRUE)

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

  object: an object of class 'drc'.

  strVal: a name of parameter to compare.

operator: a character. If equal to "/" (default) parameter ratios are
          compared. If equal to "-" parameter differences are compared.

      od: logical. If TRUE adjustment for over-dispersion is used.

    pool: logical. If TRUE curves are pooled. Otherwise they are not.
          This argument only works for models with independently fitted
          curves as specified in 'drm'.

 display: logical. If TRUE results are displayed. Otherwise they are
          not (useful in simulations).

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

     The function compares actual parameter estimates, and therefore
     the results depend on the parameterisation used. Probably it is
     most useful in combination with 'collapse' arguments (in 'drm')
     that are data frames or lists with formulas without intercept
     (-1).

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

     A matrix with columns containing the estimates, estimated standard
     errors, values of t-statistics and p-values for the null
     hypothesis that  the ratio equals 1 or that the difference equals
     0 (depending on the 'operator' argument). 

     No adjustment for multiplicity is applied. See 'p.adjust' on how
     to do adjust p-values.

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

     Christian Ritz

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

     # Fitting a model with names assigned to the parameters!
     spinach.m1 <- drm(SLOPE~DOSE, CURVE, data = spinach,
     fct = LL.4(names = c("b", "lower", "upper", "ed50")))

     ## Calculating ratios of parameter estimates for the parameter named "ed50"
     compParm(spinach.m1, "ed50")      

     ## Calculating differences between parameter estimates for the parameter named "ed50"
     compParm(spinach.m1, "ed50", "-")  

