epgcog                  package:emu                  R Documentation

_E_l_e_c_t_r_o_p_a_l_a_t_o_g_r_a_p_h_i_c _c_e_n_t_r_e _o_f _g_r_a_v_i_t_y

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

     Calculate the centre of gravity in palatographic data.

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

     epgcog (epgdata, weights = seq(7.5, 0.5, by = -1), rows = 1:8, 
         columns = 1:8, row1 = NULL) 

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

 epgdata: An eight-columned EPG-compressed trackdata object, or an
          eight columned matrix of EPG-compressed trackdata, or a 3D
          palatographic array that is the output of palate() 

 weights: A vector of 8  values  that are applied to EPG rows 1-8
          respectively. Defaults to 7.5, 7.0, 6.5...0.5. 

    rows: Calculate EPG-COG over selected row number(s). rows = 5:8,
          columns = 3:6 is an implementation of posterior centre of
          gravity, as defined by Gibbon & Nicolaidis (1999,p. 239). See
          examples below. 

 columns: Calculate EPG-COG over selected column number(s). 

    row1: an optional single valued numeric vector  to allow a separate
          weighting of the electrodes in row1. For example, if
          row1=4/3,  then all the electrodes in row1 are multiplied by 
          that value, before EPG-COG is calculated. Defaults to NULL
          (no weighting). 

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

     The centre of gravity is a key function in palatographic research
     and gives an value per palate that is indicative of the overall
     location of contacts along the anterior-posterior dimension. The
     formula is an implementation of the ones discussed in Hardcastle
     et al. (1991), Gibbon et al (1993), and Gibbon & Nicolaidis
     (1999).

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

     These functions return a trackdata object if they are applied to
     an eight-columned EPG-compressed trackdata object, otherwise a
     one-columned matrix.

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

     Jonathan Harrington

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

     GIBBON, F., HARDCASTLE, W. and NICOLAIDIS, K. (1993) Temporal and
     spatial aspects of lingual coarticuation in /kl/ sequences: a
     cross-linguistic investigation. Language & Speech, 36, 26t1-277.

     GIBBON, F. AND NICOLAIDIS, K. (1999). Palatography.  In W.J.
     Hardcastle & N. Hewlett (eds). Coarticulation.  (pp. 229-245).
     Cambridge University Press: Cambridge.

     HARDCASTLE, W, GIBBON, F. and NICOLAIDIS, K. (1991) EPG data
     reduction methods and thier implications for studies of lingual
     coarticulation. Journal of Phonetics, 19, 251-266.

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

     'epgai' 'epgsum' 'palate'

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

     #  COG: trackdata
     cog <- epgcog(coutts.epg)
     #  cog, one-columned matrix
     cog <- epgcog(dcut(coutts.epg, 0.5, prop=TRUE))
     # posterior cog for Fig. 10.5, p. 239 in Gibbon & Nicolaidis (1999)
     r = array(0, c(8, 8, 2))
     r[6,c(1, 8),1] <- 1
     r[7,c(1, 2, 7, 8), 1] <- 1
     r[8, ,1] <- 1
     r[4, c(1, 2, 8), 2] <- 1
     r[5, c(1, 2, 7, 8), 2] <- 1
     r[6, c(1, 2, 3, 7, 8), 2] <- 1
     r[7:8, , 2] = 1
     class(r) <- "EPG"
     epgcog(r, rows=5:8, columns=3:6)

