ascribe zeros to an array

I am new to matlab. I want to ascribe zeros to frequencies going from 1001 to 2048 after having built a spectrum from 1 to 1000.

How do I do it please.

f= 1001:2048;

[Rik]

Have a read here and here. It will greatly improve your chances of getting an answer.

If you have trouble with Matlab basics you may consider doing the Onramp tutorial (which is provided for free by Mathworks).

[Nuks Kar]

Thank you very much.

Answer 1

[Walter Roberson]

frequencies = linspace(0, 2400, 250);

spectrum = rand(size(frequencies));
subplot(2,1,1); plot(frequencies, spectrum); title('before zeroing');

spectrum(frequencies >= 1001 & frequencies <= 2048) = 0;

subplot(2,1,2); plot(frequencies, spectrum); title('after zeroing')

[Nuks Kar]

Thanks a lot.

Answer 2

[Bruno Luong]

To pad a vector with zeros you only need to set the last-element of the extended vector to 0

f=rand(1,5) % 1000 in your case

f = 1×5

0.7012 0.5664 0.9478 0.7397 0.8932

fpad = f; fpad(8)=0; fpad % 2048 in your case

fpad = 1×8

0.7012 0.5664 0.9478 0.7397 0.8932 0 0 0

Note that is you call fft/ifft on fpad, you don't even need to construct it, fft and ifft has the length in second argument that you can use to do fft on padded array without explicitly constructing it. Both of these return the same result

fft(fpad)

ans = 
   3.8485 + 0.0000i  -0.3146 - 1.8714i   0.6467 + 0.1733i  -0.0694 + 0.0243i   1.2362 + 0.0000i  -0.0694 - 0.0243i   0.6467 - 0.1733i  -0.3146 + 1.8714i

fft(f,8)

ans = 
   3.8485 + 0.0000i  -0.3146 - 1.8714i   0.6467 + 0.1733i  -0.0694 + 0.0243i   1.2362 + 0.0000i  -0.0694 - 0.0243i   0.6467 - 0.1733i  -0.3146 + 1.8714i