obspy.signal.filter.lowpass

lowpass(data, freq, df, corners=4, zerophase=False, rp=None, rs=None, ftype='butter', axis=-1)[source]

Lowpass Filter.

Filter data removing data over certain frequency freq using corners corners. The filter uses scipy.signal.iirfilter() (for design) and scipy.signal.sosfilt() (for applying the filter).

Parameters:

  • data (numpy.ndarray) – Data to filter.

  • freq – Filter corner frequency.

  • df – Sampling rate in Hz.

  • corners – Filter corners / order.

  • zerophase – If True, apply filter once forwards and once backwards. This results in twice the number of corners but zero phase shift in the resulting filtered trace.

  • rp – For Chebyshev and elliptic filters, provides the maximum ripple in the passband. (dB)

  • rs – For Chebyshev and elliptic filters, provides the minimum attenuation in the stop band. (dB)

  • ftype –

    The type of filter

    • Butterworth : ‘butter’ (default)

    • Chebyshev I : ‘cheby1’

    • Chebyshev II : ‘cheby2’

    • Cauer/elliptic: ‘ellip’

    • Bessel/Thomson: ‘bessel’

  • axis – The axis of the input data array along which to apply the linear filter. The filter is applied to each subarray along this axis. Default is -1.

Returns:

Filtered data.