why do i get "Array indices must be positive integers or logical values " and how do i solve it ?

theta = [0:23] * pi/12 + 3*pi/8;

x = ones(1, 24) + sin(theta);

X = fft(x) / 24;

X_period = X([-11:12]);

disp('X[k] for one period =');

disp(X_period);

Array indices must be positive integers or logical values.

[Dyuman Joshi]

As the error message states - "Array indices must be positive integers or logical values."

X_period = X([-11:12]);

Here, you have provided negative values and 0 as indices, which is not allowed. That's why you get the error.

To resolve the error, don't provide values that are not allowed.

Answer 1

[cr]

your X_period should equal to

X(1:24)

If you want to view it shifted you can have

idx = -11:12;

and either use

plot(idx,X)

or if you rather just display the numbers in text,

[idx; X]'

[Steven Lord]

0 is not a valid linear index in MATLAB. Linear indices must be positive integer values, not non-negative.

[cr]

Oops. Thanks for pointing out the oversight. Corrected it.