plafit {emuR}

Calculate the coefficients of a parabola

Description

Fit a second ordered polynomial to a vector of values

Usage

plafit(wav, fit = FALSE, n = 101)

Arguments

wav

a vector or single column matrix of numeric values to which the 2nd order polynomial is to be fitted.

fit

if FALSE, return the coefficients of the polynomial; if TRUE, the values of the polynomial are returned to the same length as the vector wav.

n

in fitting the polynomial, linear time normalisation is first applied to the input vector wav to 101 points. The polynomial is fitted under the assumption that these points extend linearly in time between t = -1 and t = 1 with t = 0 occurring at the temporal midpoint.

Details

The function fits a parabola (2nd order polynomial) following the method of van Bergem, Speech Communication, 14, 1994, 143-162. The algorithm fixes the parabola at the onset, midpoint, and offset of the vector i.e. such htat the fitted parabola and original vector have the same values at these points.

Value

The function returns the coefficients of c0, c1, c2 in the parabola y = c0 + c1t + c2t\mbox{\textasciicircum}2 where t extends between -1 and 1. The function can also be used to derive the values of the parabola as a function of time from the coefficients.

Author(s)

Jonathan Harrington

See Also

dct

Examples

# fit a polynomial to a segment of fundamental frequency data
plafit(vowlax.fund[1,]$data)

# return the fitted values of the polynomial
plafit(vowlax.fund[1,]$data, fit=TRUE)