epgcog: Electropalatographic centre of gravity

Description

Calculate the centre of gravity in palatographic data.

Usage

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

Value

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

Arguments

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).

Author

Jonathan Harrington

Details

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).

References

GIBBON, F., HARDCASTLE, W. and NICOLAIDIS, K. (1993) Temporal and spatial aspects of lingual coarticulation 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 their implications for studies of lingual coarticulation. Journal of Phonetics, 19, 251-266.

Examples

Run this code


#  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)

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