Plot sinusoid equation of x(t)
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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.'
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1269100/image.jpeg)
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)
0 Comments
Accepted Answer
Image Analyst
on 19 Jan 2023
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))')
8 Comments
Torsten
on 20 Jan 2023
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
More Answers (2)
John D'Errico
on 19 Jan 2023
Edited: John D'Errico
on 19 Jan 2023
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.
3 Comments
Torsten
on 19 Jan 2023
Do you know what exp(2*pi*1i*t) is for t=0:5 ? So the plot result shouldn't surprise you.
Sydney Lang
on 19 Jan 2023
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?
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