filtlib.py 文件源码

def butter_low(dt_list, val, lowpass=1.0):
    import scipy.signal
    #val_mask = np.ma.getmaskarray(val)
    #dt is 300 s, 5 min
    dt_diff = np.diff(dt_list)
    if isinstance(dt_diff[0], float):
        dt_diff *= 86400.
    else:
        dt_diff = np.array([dt.total_seconds() for dt in dt_diff])
    dt = malib.fast_median(dt_diff)
    #f is 0.00333 Hz
    #288 samples/day
    fs = 1./dt
    nyq = fs/2.
    order = 3
    f_max = (1./(86400*lowpass)) / nyq
    b, a = scipy.signal.butter(order, f_max, btype='lowpass')
    #b, a = sp.signal.butter(order, (f_min, f_max), btype='bandstop')
    w, h = scipy.signal.freqz(b, a, worN=2000)
    # w_f = (nyq/np.pi)*w
    # w_f_days = 1/w_f/86400.
    #plt.plot(w_f_days, np.abs(h))

    val_f = scipy.signal.filtfilt(b, a, val)
    return val_f