I'm not sure how to fix this error Warning: Integer operands are required for colon operator when used as index. > In demo (line 147)

%convolution

y1 = conv(x,h1)*Ts; %multiply by interval Ts to get integral

Nsamps = length(y1); %Nsamps is the length of array y1

t = (Ts)*(1:Nsamps); %Prepare time data for plot

figure

plot(t,y1);

xlim([1.5 1.51]); %only plot t within xlim

xlabel('Time (s)');

ylabel('Amplitude');

title('Convolution with 200Hz Cutoff');

%Do Fourier Transform of the 200Hz Cutoff signal

y_fft = abs(fft(y1 * 5)/Fs); %Normalize the signal & Retain Magnitude

y_fft = (y_fft(1:Nsamps/2)); %Discard Half of Points

f = Fs*(0:Nsamps/2-1)/Nsamps; %Prepare freq data for plot

[Bobby]

line 147 is

y_fft = (y_fft(1:Nsamps/2)); %Discard Half of Points

Answer 1

[Voss]

This is probably due to the fact that Nsamps is odd, so that Nsamps/2 is not an integer, so that this line:

y_fft = (y_fft(1:Nsamps/2));           %Discard Half of Points

produces the warning. It's just a warning (not an error), so you don't need to 'fix' it, but you can avoid it by only using integers with the colon operator when used as indexes. For instance:

if rem(Nsamps,2) == 1
    y_fft = y_fft(1:(Nsamps-1)/2);
else
    y_fft = y_fft(1:Nsamps/2);
end

or, equivalently:

y_fft = y_fft(1:(Nsamps-rem(Nsamps,2))/2);