xdas.signal.decimate#

xdas.signal.decimate(da, q, n=None, ftype='iir', zero_phase=True, dim='last', parallel=None)[source]#

Downsample the signal after applying an anti-aliasing filter.

By default, an order 8 Chebyshev type I filter is used. A 30 point FIR filter with Hamming window is used if ftype is ‘fir’.

Parameters:

  • da (DataArray) – The signal to be downsampled, as an N-dimensional dataarray.

  • q (int) – The downsampling factor. When using IIR downsampling, it is recommended to call decimate multiple times for downsampling factors higher than 13.

  • n (int, optional) – The order of the filter (1 less than the length for ‘fir’). Defaults to 8 for ‘iir’ and 20 times the downsampling factor for ‘fir’.

  • ftype (str {‘iir’, ‘fir’} or dlti instance, optional) – If ‘iir’ or ‘fir’, specifies the type of lowpass filter. If an instance of an dlti object, uses that object to filter before downsampling.

  • dim (str, optional) – The dimension along which to decimate.

  • zero_phase (bool, optional) – Prevent phase shift by filtering with filtfilt instead of lfilter when using an IIR filter, and shifting the outputs back by the filter’s group delay when using an FIR filter. The default value of True is recommended, since a phase shift is generally not desired.

  • parallel (bool or int, optional) – Number of threads to use. True uses all cores, False uses one, an int uses that many, None defers to the global xdas configuration. Default is None.

Returns:

The down-sampled signal.

Return type:

DataArray

Notes

Splits on data discontinuities along dim.