Fourth order kernel polynomial Wigner-Ville distribution Computes the 4th order Kernel pwvd of the input signal. An analytic signal generator is called if the input signal is real. This version takes advantage of the reality of the pwvd to increase calculation speed. Usage: tfd = pwvd4( signal, lag_window_length, time_res [, fft_length] ) Parameters: tfd The computed time-frequency distribution. size(tfd) will return [a, b], where a is the next largest power of two above lag_window_length, and b is floor(length(signal)/time_res) - 1. signal Input one dimensional signal to be analysed. An analytic signal is required for this function, howver, if signal is real, a default analytic transformer routine will be called from this function before computing tfd. lag_window_length The size of the kernel used for analysis lag_window_length must be odd. The kernel used will be defined from -(lag_window_length+1)/2 to +(lag_window_length+1)/2 in both time and lag dimensions. time_res The number of time samples to skip between successive slices of the analysis. fft_length Zero-padding at the fft stage of the analysis may be specified by giving an fft_length larger than normal. If fft_length is not specified, or is smaller than the lag_window_length, then the next highest power of two above data_data_window_length is used. If fft_length is not a power of two, the next highest power of two is used. See Also: pwvd6