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scipy.signal.tf2sos(b, a, pairing='nearest')[source]

Return second-order sections from transfer function representation


b : array_like

Numerator polynomial coefficients.

a : array_like

Denominator polynomial coefficients.

pairing : {‘nearest’, ‘keep_odd’}, optional

The method to use to combine pairs of poles and zeros into sections. See zpk2sos.


sos : ndarray

Array of second-order filter coefficients, with shape (n_sections, 6). See sosfilt for the SOS filter format specification.

See also

zpk2sos, sosfilt


It is generally discouraged to convert from TF to SOS format, since doing so usually will not improve numerical precision errors. Instead, consider designing filters in ZPK format and converting directly to SOS. TF is converted to SOS by first converting to ZPK format, then converting ZPK to SOS.

New in version 0.16.0.