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Hd = dfilt.dffir(b)
Hd = dfilt.dffir
Hd = dfilt.dffir(b) returns a discrete-time, direct-form finite impulse response (FIR) filter, Hd, with numerator coefficients, b.
Hd = dfilt.dffir returns a default, discrete-time, direct-form FIR filter, Hd, with b=1. This filter passes the input through to the output unchanged.

The resulting filter states column vector is
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Create a direct-form FIR discrete-time filter with coefficients from a 30th order lowpass equiripple design:
b = firpm(30,[0 .1 .2 .5]*2,[1 1 0 0]);
Hd = dfilt.dffir(b)
Hd =
FilterStructure: 'Direct-Form FIR'
Numerator: [1x31 double]
PersistentMemory: false
dfilt, dfilt.dfasymfir, dfilt.dffirt, dfilt.dfsymfir
![]() | dfilt.dfasymfir | dfilt.dffirt | ![]() |
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