how to set limits of integration (for example: 0:inf) for a vector using trapz tool ?

%defining a linear modulated signal

Fs = 1000; % Sampling frequency

T = 1/Fs; % Sample time

L = 5000; % Length of signal

t = (0:L-1)*T; % Time vector

a=chirp(t,5,max(t),20,'linear');

f=fft(a);

F=(0:L-1)/Fs;

e=trapz(F,(abs(f).^2));

%finding the average frequency

x=trapz(F,F.*abs(f).^2);

AVG=x./e

Answer 1

[Daniel M]

Your vector of frequencies is not correct, because fft returns the negative frequencies first, followed by the positive frequencies. I suggest looking at the documentation for fft.

https://www.mathworks.com/help/matlab/ref/fft.html

Otherwise, trapz will integrate over whatever values you provide it. If you want it to integrate over a certain interval, only pass those elements as inputs. You can also look into integral().

https://www.mathworks.com/help/matlab/ref/integral.html

Correction: fft returns the frequencies in the following order: zeroth frequency, positive frequencies up to the Nyquist freq, followed by the negative frequencies in ascending order.

[mavi gul]

thank you very much