# help me with for loop

2 views (last 30 days)
nirwana on 15 Sep 2023
Answered: William Rose on 23 Sep 2023
I know this is very basic question, but i still has difficulty to answer it
i try to add some fourier series to prove gibbs effect
here my coding
t=0:0.01:7;
%odd series
yo= sin(t) + sin(3*t)/3 + sin(5*t)/5 + sin(7*t)/7 + sin(9*t)/9+sin(11*t)/11;
yoo=sin(13*t)/13+sin(15*t)/15+sin(17*t)/17+sin(19*t)/19+sin(21*t)/21;
subplot(211), plot(t,(yo+yoo)),title('fourier odd series')
%even series
ye= sin(0*t) + sin(2*t)/2 + sin(4*t)/4 + sin(6*t)/6 + sin(8*t)/8+sin(10*t)/10;
subplot(212), plot(t,ye), title('fourier even series')
instead of putting long equation, i would like to put it in for loop. can you help me to "rearange" my code neatly in foor loop.
my other question is : which one better to do it, for loop or vectorization (my teacher said that foor loop) must be avoid because it slower computational time
Stephen23 on 15 Sep 2023
Edited: Stephen23 on 15 Sep 2023
"which one better to do it, for loop or vectorization (my teacher said that foor loop) must be avoid because it slower computational time"
For such a simple calculation I doubt there would be much difference. Overall (code runtime + write time + debug time + maintenance time) vectorized code is more efficient: you already have it and presumably it does what you want.
But go ahead: test them both and let us know.
"instead of putting long equation, i would like to put it in for loop. can you help me to "rearange" my code neatly in foor loop."
There are two posisble things you could loop over: 1) the elements of t or 2) the terms of the fourier series: which one do you want to loop over?

William Rose on 23 Sep 2023
@Stephen23 knows more about Matlab than almost anybody. When he says "I doubt there is much of a difference", I think he knows the answer and he is encouraging you to find out for yourself.
Your other question was how to replace a line such as
t=(0:.01:2)*2*pi;
yo= sin(t) + sin(3*t)/3 + sin(5*t)/5 + sin(7*t)/7 + sin(9*t)/9+sin(11*t)/11;
with a for loop.
yoloop=0;
for i=1:2:11
yoloop=yoloop+sin(i*t)/i;
end
Plot result
plot(t,yo,'-rx',t,yoloop,'-go');
legend('yo','yoloop')
You can see the GIbbs effect. Try this idea for yoo and ye.