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    %% Transfer Function Between Two Sequences
% Compute and plot the transfer function estimate between two sequences,
% |x| and |y|. |x| consists of white Gaussian noise. |y| results from
% filtering |x| with a 30-th order lowpass filter with normalized cutoff
% frequency $0.2\pi$ rad/sample. Use a rectangular window to design the
% filter. Specify a sample rate of 500 Hz and a Hamming window of length
% 1024 for the transfer function estimate.

% Copyright 2015 The MathWorks, Inc.


%%

h = fir1(30,0.2,rectwin(31));
x = randn(16384,1);
y = filter(h,1,x);

fs = 500;
tfestimate(x,y,1024,[],[],fs)

%%
% Use |fvtool| to verify that the transfer function approximates the
% frequency response of the filter.

fvtool(h,1,'Fs',fs)

%%
% Obtain the same result by returning the transfer function estimate in a
% variable and plotting its absolute value in decibels.

[Txy,f] = tfestimate(x,y,1024,[],[],fs);

plot(f,mag2db(abs(Txy)))