attrassign             package:survival             R Documentation

_C_r_e_a_t_e _n_e_w-_s_t_y_l_e "_a_s_s_i_g_n" _a_t_t_r_i_b_u_t_e

_D_e_s_c_r_i_p_t_i_o_n:

     The '"assign"' attribute on model matrices describes which columns
     come from which terms in the model formula. It has two versions. R
     uses the original version, but the alternate version found in
     S-plus is sometimes useful.

_U_s_a_g_e:

     ## Default S3 method:
     attrassign(object, tt,...)
     ## S3 method for class 'lm':
     attrassign(object,...)

_A_r_g_u_m_e_n_t_s:

  object: model matrix or linear model object

      tt: terms object

     ...: ignored

_D_e_t_a_i_l_s:

     For instance consider the following


         survreg(Surv(time, status) ~ age + sex + factor(ph.ecog),
     lung)

     R gives the compact for for assign, a vector (0, 1, 2, 3, 3, 3);
     which can be read as ``the first column of the X matrix
     (intercept) goes with none of the terms, the second column of X
     goes with term 1 of the model equation, the third column of X with
     term 2, and columns 4-6 with term 3''.

     The alternate (S-Plus default) form is a list


            $(Intercept)     1
            $age             2
            $sex             3
            $factor(ph.ecog) 4 5 6


_V_a_l_u_e:

     A list with names corresponding to the term names and elements
     that are vectors indicating which columns come from which terms

_S_e_e _A_l_s_o:

     'terms','model.matrix'

_E_x_a_m_p_l_e_s:

     formula <- Surv(time,status)~factor(edema)
     tt <- terms(formula)
     mf <- model.frame(tt,data=pbc)
     mm <- model.matrix(tt,mf)
     ## a few rows of data
     mm[1:3,]
     ## old-style assign attribute
     attr(mm,"assign")
     ## alternate style assign attribute
     attrassign(mm,tt)