_stockwell.py 文件源码

def _precompute_st_windows(n_samp, start_f, stop_f, sfreq, width):
    """Precompute stockwell gausian windows (in the freq domain)"""
    tw = fftpack.fftfreq(n_samp, 1. / sfreq) / n_samp
    tw = np.r_[tw[:1], tw[1:][::-1]]

    k = width  # 1 for classical stowckwell transform
    f_range = np.arange(start_f, stop_f, 1)
    windows = np.empty((len(f_range), len(tw)), dtype=np.complex)
    for i_f, f in enumerate(f_range):
        if f == 0.:
            window = np.ones(len(tw))
        else:
            window = ((f / (np.sqrt(2. * np.pi) * k)) *
                      np.exp(-0.5 * (1. / k ** 2.) * (f ** 2.) * tw ** 2.))
        window /= window.sum()  # normalisation
        windows[i_f] = fftpack.fft(window)
    return windows