MATLAB: (Beginner)Simple for-loop! Help!

arrayfor loopplot

Hello. I have what I believe is a very simple problem, that I just can't wrap my head around.
I want to plot a sine-curve and a square plot that changes between 0 and 1 as the sinus curve goes between positive and negative value. Here is my code:
x=[0:0.1:3*pi];
y=sin(x);
T = zeros(1,length(x));
for i=1:length(x)
    if(sin(i) > 0)
        T(i) = 1;
    else
        T(i) = -1;
    end
end
plot(x, y, x, T, 'r');

Best Answer

Magnarok - rather than conditioning on
 sin(i) > 0
use
 y(i) > 0
since those are the values of the sine curve. Remember, i is an integer from 1 to the length of your x array, so sin(i) is not what you want to be computing. (I suppose you could do sin(x(i)) > 0 but that seems like extra work when you already have y.)
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