How to sum a series of functions and then plot the sum?

Question

Shaun Pedicini 2018-3-1

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/385726-how-to-sum-a-series-of-functions-and-then-plot-the-sum

评论： Abraham Boayue 2018-3-5

采纳的回答： Abraham Boayue

在 MATLAB Online 中打开

This function is supposed to be able to plot a box filter:

That should possibly look like this:

I already defined t as a 1x360 double array using:

t = t = linspace(0, 4, 360)
syms k
z = symsum( (1 / k) * sin((2 * pi) * k * t ), k, 1, 10) ;

It returns a 1x360 sym variable, but I don't know how to plot it.

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Shaun Pedicini 2018-3-1

hmm, is there a way I can rewrite this without symbolic math? I have to admit to being very unfamiliar with Matlab as a whole.

I actually tried doing plot(t, z) after I posted this question and it looks like it works after all, though I'm not entirely sure.

Walter Roberson 2018-3-1

在 MATLAB Online 中打开

Z = double(z);
plot(t, Z)

Your MATLAB is detecting that the input is sym and is doing the double() on your behalf, but you can make what you are doing more obvious by doing the double() yourself.

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Answer 1

Abraham Boayue 2018-3-2

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/385726-how-to-sum-a-series-of-functions-and-then-plot-the-sum#answer_308007

在 MATLAB Online 中打开

clear variables
close all
M = 250; % The length of each function
A=3;
t = -2:4/(M-1):2;
y = zeros(1,M); % Initiallize the sum to zero
N = 100;
for k = 1:N
 ck = 1/k;
 y = y+ A*ck*sin(pi*k*t); % computing the sum
end
plot(t,y,'linewidth',2,'color','m')
a= title('y(t) : sum of sine wave');
set(a,'fontsize',14);
a= xlabel('x [-2\pi 2\pi]');
set(a,'fontsize',20);
a = ylabel('y');
set(a,'fontsize',20);
a = zlabel('z');
set(a,'fontsize',20);
grid;