find function not working with double inequality

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I am trying to use a double inequality to define in my loop which outputs to display together from my filter. I am not getting any error, but my figure 2 is showing all outputs instead of just the few which fall into the designated range. To check this specific case I looked into my array and found that figure 2 should be only displaying only output 5, 6, and 7. I am redefining my output variable to include indf which is supposed to find those outputs as they fall in that range. I am unsure what is going wrong. Thank you for your time!
close all
clear all
clc
%
fs = 20e3;
numFilts = 32; %
filter_number = numFilts;
order = 4;
CenterFreqs = logspace(log10(50), log10(8000), numFilts);
% input signal definition can increase Nperiods instead of zero padding for
% resolution
signal_freq = 1000; % Hz
Nperiods = 15; % we need more than 1 period of signal to reach the steady state output (look a the IR samples)
t = linspace(0,Nperiods/signal_freq,200*Nperiods); %
input = sin(2*pi*signal_freq*t) + 0*rand(size(t));
figure%2
hold on
for ii = 1:filter_number
IR = gammatone(order, CenterFreqs(ii), fs);
[tmp,~] = freqz(IR,1,1024*2,fs);
% scale the IR amplitude so that the max modulus is 0 dB
a = 1/max(abs(tmp));
IR_array{ii} = IR*a; % scale IR and store in cell array afterwards
[h{ii},f] = freqz(IR_array{ii},1,1024*2,fs); % now store h{ii} after amplitude correction
plot(IR_array{ii})
end
title('Impulse Response');
hold off
xlim([0 1000]);
%% 3D
figure
hold on
b=50; %bandwidth
indf = find(signal_freq-b<CenterFreqs<signal_freq+b);
for ii = 1:numel(indf)
output(ii,:) = filter(IR_array{indf(ii)},1,input);
plot3(t,ii*ones(size(t)),output(ii,:))
LEGs{ii} = ['Filter # ' num2str(indf(ii))]; %assign legend name to each
end
view(-40,60); % view angles
% display integer ticks on Y axis
ax = gca;
ax.YTick = unique(round(ax.YTick));
output_sum = sum(output,1);
% plot(t,output_sum)
% LEGs{ii+1} = ['Sum'];
legend(LEGs{:})
legend('Show')
title('Filter output signals');
xlabel('Time (s)');
ylabel('Output #');
zlabel('Amplitude');
hold off

Accepted Answer

Voss
Voss on 11 Apr 2024
Edited: Voss on 11 Apr 2024
This is not the correct way to check multiple inequalities:
indf = find(signal_freq-b<CenterFreqs<signal_freq+b);
Instead do:
indf = find( signal_freq-b<CenterFreqs & CenterFreqs<signal_freq+b );
or:
indf = find( abs(CenterFreqs-signal_freq) < b )
  10 Comments
Voss
Voss on 18 Apr 2024
indf = find(abs(CenterFreqs-(signal_freq-s)) < b );
finds elements of CenterFreqs that are within b (=50) of signal_freq-s (=850), so within the range 800 to 900, exclusive.
indf = find( abs(CenterFreqs-(signal_freq+s)) < b );
does the same within the range 1100 to 1200, exclusive.
So what you said is right, except it's 100 (which is 2*b) not 150 (which is s).
S
S on 21 Apr 2024
@Voss oh makes sense! So the first line is for lower freqs, while the second is for higher freqs. Thank you!

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