# How to plot sine graph by using for loop?

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Xing Xing on 5 Jun 2019
Commented: AZEEM IMTIAZ on 4 Aug 2019
I tried to use a for loop to plot a sine graph. The values are generated but then when I try to graph them, I get either an error or no graph. Here's my code:
for i = 0:0.1:2*pi
m=sin(i);
n=i;
plot(n,m,'-r');
hold on
end

Mohammad Alhashash on 5 Jun 2019
do you want to animate the sine graph or just plot it
Xing Xing on 5 Jun 2019
I just want to plot it with this for loop.

Alex Mcaulley on 5 Jun 2019
You don't need a loop, just:
theta = 0:0.1:2*pi;
plot(theta,sin(theta))

Alex Mcaulley on 5 Jun 2019
With your code, you are generating one point in each iteration, not a unique line. If you want to see it:
for i = 0:0.1:2*pi
m=sin(i);
n=i;
plot(n,m,'*r');
hold on
end
numel(findobj(gca,'Type','Line'))
Xing Xing on 5 Jun 2019
OH, I see! Thanks!
AZEEM IMTIAZ on 4 Aug 2019
you need to define t as a continuous variable in the first line then apply for loop on the frequency as discrete values. so that each frequency point will sweep over the time that you have defined in the first line. hope this helps!
t=0:0.04:5;
hold on
for f=[0.7 1 1.5 2]
y=cos(2*pi*f*t);
plot(t,y)
end

Mohammad Alhashash on 5 Jun 2019
maybe that is what you need.
t= 0:0.01:2*pi;
m =sin(t);
t_plot = NaN(1,length(t));
m_plot = NaN(1,length(m));
u = 1;
for i = 1:length(t)
cla
t_plot(i) = t(u);
m_plot(i) = m(u);
plot(t_plot,m_plot)
drawnow
u = u + 1;
end

#### 1 Comment

Xing Xing on 5 Jun 2019
I understand what is my problem and thank you for your answer!