what is wrong with my code, i am trying to plot below

Question

Maxwell Lane 2020-3-20

0
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https://ww2.mathworks.cn/matlabcentral/answers/512000-what-is-wrong-with-my-code-i-am-trying-to-plot-below

回答： the cyclist 2020-3-20

for t = 1:.01:10;
   if t <= pi
        x = 1.41.*exp(-t).*sin(t+0.785);
    elseif t > pi
        x = 1.41.*exp(-t).*sin(t+0.785)-(exp(-(t-pi).*sin(t-pi)));
    end
end
 
plot(t,x)   
xlabel('t')
ylabel('X(t)')

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Answer 1

the cyclist 2020-3-20

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In every iteration of the for loop, you are simply overwriting x, over and over.

Instead, you need to define a vector for x, too. Here is one way:

t = 1:.01:10;
tCount = numel(t);
x = zeros(tCount,1);
for nt = 1:tCount
   if t(nt) <= pi
        x(nt) = 1.41.*exp(-t(nt)).*sin(t(nt)+0.785);
    elseif t(nt) > pi
        x(nt) = 1.41.*exp(-t(nt)).*sin(t(nt)+0.785)-(exp(-(t(nt)-pi).*sin(t(nt)-pi)));
    end
end
 
plot(t,x)   
xlabel('t')
ylabel('X(t)')

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Answer 2

the cyclist 2020-3-20

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https://ww2.mathworks.cn/matlabcentral/answers/512000-what-is-wrong-with-my-code-i-am-trying-to-plot-below#answer_421156

在 MATLAB Online 中打开

FYI, there is a much more efficient solution, which is to avoid the for loop altogether:

t = 1:.01:10;
x = zeros(size(t));
x(t<=pi) = 1.41.*exp(-t(t<=pi)).*sin(t(t<=pi)+0.785);
x(t>pi) = 1.41.*exp(-t(t>pi)).*sin(t(t>pi)+0.785)-(exp(-(t(t>pi)-pi).*sin(t(t>pi)-pi)));
plot(t,x)   
xlabel('t')
ylabel('X(t)')