(Beginner)Simple for-loop! Help!

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');

Answer 1

[Geoff Hayes]

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.)

[Magnarok]

Thanks alot mate! :)