Plot sinusoid equation of x(t)

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collegestudent
collegestudent 2023-1-19
编辑： Torsten 2023-1-20
I am trying to solve this problem using a MATLAB. I have attached the problem itself along with the code I have written so far. When I run the code I get an error that says 'Array indices must be positive integers or logical values.'
t = 0:5;
x = sqrt(2)*(1+1i)*exp(1i*(pi/4))*exp((-1+((1i)*2*pi)*t));
re = real(x);
imaginary = imag(x);
plot(re)
hold on
plot(imaginary)

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采纳的回答

Image Analyst
Image Analyst 2023-1-19
Ran in:
This works just fine:
t = linspace(0, 5, 500);
x = sqrt(2) * (1+1i) * exp(1i*(pi/4)) * exp((-1+((1i)*2*pi)*t));
re = real(x);
imaginary = imag(x);
plot(re, 'b-', 'LineWidth', 2)
hold on
plot(imaginary, 'r-', 'LineWidth', 2)
legend('Real Part', 'Imaginary Part', 'Location', 'northwest')
grid on;
xlabel('t');
ylabel('x real or imaginary part')
title('x = sqrt(2) * (1+1i) * exp(1i*(pi/4)) * exp((-1+((1i)*2*pi)*t))')
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collegestudent
collegestudent 2023-1-20
编辑：collegestudent 2023-1-20
But I already have x defined so I should rename it to be say xt when defining it as a function handle?
Update I added your suggestion to define x but it did not plot x(t+2)+x*(t+2)
Torsten
Torsten 2023-1-20
Ran in:
x = @(t)sqrt(2) * (1+1i) * exp(1i*(pi/4)) * exp((-1+(1i)*2*pi)*t);
t = linspace(-2, 2, 400);
hold on
plot(t,real(x(t)))
plot(t,imag(x(t)))
plot(t,x(t+2)+conj(x(t+2)))
hold off
grid on

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更多回答（2 个）

John D'Errico
John D'Errico 2023-1-19
编辑：John D'Errico 2023-1-19
Do not define a variable with the names: sqrt, exp, real, imag, plot
If you do, then what do you think will happen when you then try to use the functions of the same name? Should MATLAB know what you want it to do? Sorry, but computers are very literal things. They try to do what you tell them to do. But when you tell them to do something confusing, what do you expect?
Do this at the command line:
which sqrt -all
which exp -all
which real -all
which imag -all
which plot -all
One of those will tell you that you have created a variable by that name. Delete the offending variable. My guess would be the problem lies in one of the names exp, real, or imag.
You could also have just looked at the list of variable names. So my guess is this would tell you something useful:
whos exp real imag
As if any of those variable names were used by you, they would now show up.
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Torsten
Torsten 2023-1-19
Do you know what exp(2*pi*1i*t) is for t=0:5 ? So the plot result shouldn't surprise you.
collegestudent
collegestudent 2023-1-19
the time vector of t = 0:5; is not given in the equation. I just set it to be that for testing purposes, howeer the plot should be a sin wave with envolopes

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Sydney Lang
Sydney Lang 2023-1-19
You haven't defined t. If you do, the code works.
Additionally you haven't mentioned where this error occurs. I assume its coming from how you defined t?
  1 个评论
collegestudent
collegestudent 2023-1-19
I adjusted my code but the error still occurs along with an error at line 5
t = 0:5;

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