how to plot a periodic function fro negative to positive?

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Daniel Niu
Daniel Niu 2022-10-20
评论： Sam Chak 2022-10-20
Dear friend,
How to plot a periodic function for example 2*x from negative to positive?
I know a method to plot periodic function using mod but, It seems can not plot the negative range.
t = 10; % total simulation time
T = 3; % period
x = 0:0.1:t;
% lets say your original function is y=2*x which repeated every T second, then
y = 2*(mod(x,T));
plot(x,y)
However, because the mod of negative is a little strange, I don't know how to modify the code.
Your help would be highly appreciated
  2 个评论
Daniel Niu
Daniel Niu 2022-10-20
Dear Mr Reddy,
The answer is not what I want. for example. I want my function at -pi:pi periodic. But the method only can plot function in 0:2pi.
I am looking forward to your reply.
Best regards.

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采纳的回答

Torsten
Torsten 2022-10-20
Ran in:
T = pi; % period
x = -10:0.1:10;
% lets say your original function is y=2*x which repeated every T second, then
y = 2*(mod(x-pi,2*pi)-pi);
plot(x,y)
grid on

更多回答（1 个）

Sam Chak
Sam Chak 2022-10-20
编辑：Sam Chak 2022-10-20
Ran in:
Hi @Daniel Niu
Are you looking for this?
Edit: Made changes as per shown in your diagram. Because the amplitude is unknown, then you need to multiply the function by a certain factor to get the desired amplitude.
t = 3*pi; % total simulation time
T = 2*pi; % period (from -π to +π) --> π - (-π) = 2π
x = -t:0.01:t;
y = 2*(mod((x - pi), T)) - 2*T/2; % also need to shift x by pi
plot(x/pi, y), grid on,
xlabel('{$\frac{x}{\pi}$}', 'interpreter', 'latex', 'fontsize', 16)
ylabel('{$y$}', 'interpreter', 'latex', 'fontsize', 16)
  3 个评论
显示 1更早的评论
Daniel Niu
Daniel Niu 2022-10-20
Dear Mr Chak,
I am looking something like this.
Thank you so much for your answers.
Sam Chak
Sam Chak 2022-10-20
Don't mention it @Daniel Niu. I have edited the code to display the sawtooh wave as per your sketched diagram. If you find the solution is helpful, please consider accepting ✔ and voting 👍 the Answer. Thanks!

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