Adding k discrete functions together in a "for" loop

Hello,

I'm trying to create a loop that creates individual discrete sine waves from a vector of sampled frequencies (locs), then adds those values together to create a single combined waveform.

My code worked well symbolically:

syms tau

locs = [440 529 630] %example frequencies

combined = 0;

for k = 1:length(locs)
    figure
    hold on
    wave(k) = sin(2*pi*locs(k)*tau); %generate sin wave for each sampled frequency
    fplot(sin(2*pi*locs(k)*tau),[0 0.01])
    hold off
    combined = combined + wave(k); %add each generated sin wave to the previous one
end

figure
fplot(combined, [0 0.01])

But I am having trouble converting it to a discrete form. I get an error that says the indices on the left do not match the indices on the right, which I assume means that I am trying to put a 132300 element array (the sin function of t) into a 1x3 array (wave(k)).

t = 0:1/44100:3;

locs = [440 529 630] %example frequencies

combined = 0;

for k = 1:length(locs)
    figure
    hold on
    wave(k) = sin(2*pi*locs(k)*t); %generate sin wave for each sampled frequency
    stem(sin(2*pi*locs(k)*t),[0 441]) 
    hold off
    combined = combined + wave(k); %add each generated sin wave to the previous one
end

figure
stem(combined, [0 441])

Is there a better way to handle/store each of the generated sin waves so they can be added together in a discrete form?

Answer 1

[Vladimir Sovkov]

If you do not need the "wave" contents for a further use, just drop out (k) from all its entries.

If you need it for a further use, initialize it as

wave=zeros(3,numel(t));

before the loop and address it as wave(k,:) within the loop.

Commands "stem" are definitely incorrect. If you want to see plots of the dependences on t, they should look something like stem(t,combined) or plot(t,combined), etc. However, the t range in the second version (0,3) is much wider than the one of the first version (0,0.01): consequently, such a graph will show much (hugely) more oscillations--you will probably see nothing but a unifromly painted square.

I do not see any need in the "nold on" and "hold off" commands in the both version.