Figure Output blank but no errors

I am trying to plot the frequency response of all of the outputs as shown below, for some reason figure 2 is just blank. I have no errors so I am unsure what is wrong. Thanks for your time!

close all
fs = 20e3; 
numFilts = 32;
filter_number = 5;
CenterFreqs = logspace(log10(50), log10(8000), numFilts);
t = linspace(0,2*pi,200);
input = sin(t) + 0.25*rand(size(t));
% 
figure
hold on

for ii = 1:filter_number
    output = gammatone(input, CenterFreqs(ii), fs);
    plot(output)
end

Unrecognized function or variable 'gammatone'.

figure
[h{ii},f] = freqz(output(ii),1,4*8192,fs);

Answer 1

[Aquatris]

When you call freqz with outputs, it does not draw a plot as written on the description of the function. So you need to do

[h,w] = freqz(b,a,'whole',2001);
plot(w/pi,20*log10(abs(h))) % specific call to plot

as shown in the documentation. If you open the freqz function code and check line 174 (Matlab 2023a) you will also see it only plots if there are no output arguments.

[S]

what is b and what is a? Also does freqz not already take care of the 20log10 abs part?

[Aquatris]

They are the basic inputs to the function. You called the freqz function with

[h{ii},f] = freqz(output(ii),1,4*8192,fs);

so just call

plot(f/pi,20*log10(abs(h{ii})))

and it should give you the plot for ii

[S]

I initially had the freqz line you just recommended and it gives a blank plot.

[h{ii},f] = freqz(output(ii),1,4*8192,fs);

plot(f/pi,20*log10(abs(h{ii})));

[S]

I was just testing higher filter_number values and for some reason they just give a singular flat horizontal line which is incorrect

[Aquatris]

Ye hard to tell since I dont know what your gammatone function does. What is inside the 'output' variable? Is it something expected?

Do you really have '1' as your denominator of interest?

Are you by any chance trying to find the frequency content, something like fft?

[S]

This is my function:

% Function for gammatone filter

function output = gammatone(input, centerFrequency, fs)

The output variable is what comes out of each individual filter. (The output of one filter is the input to the next)

[Aquatris]

Then if I understood it correctly, output variable contains a signal not the filter. However freqz function expects the numerator and denominator of a filter (transfer function). Are you trying to plot the fft of the output variable? Can you explain what you are trying to do and what you expect in the output variable again?

[S]

So I changes the line for output to this hoping it would fix it. What I want is for each output to be graphed. Since they are in cascade the output of one is the input to the next, so I am trying to plot all the outputs of every filter number. What I have below is not working though

output(ii,:) = gammatone(input, CenterFreqs(ii), fs);

plot(t,output(ii,:), 'LineWidth', 1.25)

[Aquatris]

Define not working? What do you expect and what is happenig? What do you have in output variable?

Are you sure your gammatone function works properly?

Be more specific otherwise no one can help you.