Trying to plot a periodic function

Not sure how to fix this error please assist

t=0:0.1:1000

ao=0.504

for n=1:1000

an=0.504*(2/(1+16*(n^2)));

bn=0.504*((8*n)/(1+16*(n^2)));

f(t)=ao + (an*cos(2*n*t))+(bn*sin(2*n*t))

end

plot(t,f(t));

here is my error

Subscript indices must either be real positive integers or logicals.

Error in asda (line 6)
    f(t)=ao + (an*cos(2*n*t))+(bn*sin(2*n*t))

Answer 1

[Star Strider]

First, MATLAB requires that subscripts (and indices) be integers greater than zero, so using ‘t’ as an index variable will not work.

Second, your ‘f’ calculation is vectorised at each iteration, producing a (1x10001) row vector. If you want to calculate and store all of them for each iteration of ‘n’, you have to account for that in your indexing.

Try this:

f(n,:)=ao + (an*cos(2*n*t))+(bn*sin(2*n*t));

with the plot call then being simply:

plot(t,f)

[Christopher Carey]

this doesn't seem to give me the desired signal

[Star Strider]

I only addressed the problem you asked for help with.

This appears to be an inverse Fourier transform. Consider changing the ‘f’ calculation by not adding ‘ao’ at each step, then calculating the sum of the ‘f’ matrix at the end, and adding ‘ao’ to that result.

Check the expression for the inverse Fourier transform, since you may have omitted some necessary details in your code.

[Christopher Carey]

I can show you the desired signal if wish to look and see if my code corresponds to that signal or now

[Star Strider]

You did not define ‘t’ correctly.

Try this:

t = linspace(0, pi, 250);

as well as my earlier suggestions. You might want to extend ‘t’ for a few cycles to see that the waveform repeats periodically, as it should. I will let you experiment with that.