Discrete-time, direct-form I transposed filter
Hd = dfilt.df1t(b,a)
Hd = dfilt.df1t
Hd = dfilt.df1t(b,a) returns a discrete-time, direct-form I transposed filter, Hd, with numerator coefficients b and denominator coefficients a. The filter states for this object are stored in a filtstates object.
To display the filter states, use this code to access the filtstates object.
Hs = Hd.states % Where Hd is the dfilt.df1 object and double (Hs) % Hs is the filtstates object
The vector of states is:
Alternatively, you can access the states in the filtstates object:
b = [0.05 0.9 0.05]; Hd = dfilt.df1t(b,1); Hd.States % Returns % Numerator: [2x1 double] % Denominator: [0x1 double] Hd.States.Numerator(1)=1; %Set zb(1) equal to 1.
Create a direct-form I transposed discrete-time filter with coefficients from a fourth-order lowpass Butterworth design:
[b,a] = butter(4,.5); Hd = dfilt.df1t(b,a)