ss="comment"> APSDSP  Power Spectral Density, PSD, by smoothed periodogram

           [Pxx,f,Nw] = apsdsp(x,fs,N,winstr) produces a linear
                        resolution PSD, similar to APSDW
           [Pxx,f,Nw] = apsdsp(x,fs,fmin,fmax,Nfreqs,Lsmin,winstr) produces a logartihmic
                        frequency resolution PSD

            Pxx        PSD in units of x squared per Hz (EU^2/Hz)
            f          Frequency axis in Hz
            Nw         Length of smoothing window. Determines ran