autism                package:WWGbook                R Documentation

_a_u_t_i_s_m _d_a_t_a _i_n _C_h_a_p_t_e_r _6

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

     The data comes from researchers at the University of Michigan as
     part of a prospective longitudinal study of 214 children.

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

     data(autism)

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

     A data frame with 612 observations on the following 4 variables.

     _a_g_e : Age in years (2, 3, 5, 9, 13); the time variable

     _v_s_a_e : Vineland Socialization Age Equivalent: parent-reported
          socialization, the dependent variable measured at each age

     _s_i_c_d_e_g_p : Sequenced Inventory of Communication Development
          Expressive Group: categorized expressive language score at
          age 2 years (1 = Low, 2 = Medium, 3 = High)

     _c_h_i_l_d_i_d : Unique child identifier

_R_e_f_e_r_e_n_c_e_s:

     Oti, R., Anderson, D., Risi, S., Pickles, A. & Lord, C., Social
     Trajectories Among Individuals with Autism Spectrum Disorders, 
     Developmental Psychopathology (under review), 2006.

     West, B., Welch, K. & Galecki, A, Linear Mixed Models: A Practical
     Guide Using Statistical Software, Chapman Hall / CRC Press, first
     edition, 2006.

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

     attach(autism)

     ###Figure 6.1: Observed VSAE values plotted against age for children in each SICD group. 

     sicdegp.f <- factor(sicdegp)
     age.f <- factor(age)

     # Add the new variables to a new data frame object.
     autism.updated <- data.frame(autism, sicdegp.f, age.f)

     library(lattice)  # Load the library for trellis graphics.
      
     # Load the nlme library, which is required for the 
     # plots below as well as for subsequent models.
     library(nlme)

     autism.g1 <- groupedData(vsae ~ age | childid, 
     outer = ~ sicdegp.f, data = autism.updated)

     plot(autism.g1, display = "childid", outer = TRUE, aspect = 2, key = FALSE, xlab = "Age (Years)", ylab = "VSAE", 
     main = "Individual Data by SICD Group") 

