How to plot complex signal

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Tiam Huat Goh
Tiam Huat Goh on 25 Oct 2014
Commented: Image Analyst on 28 Feb 2023
I'm very new to MatLab, how do i write a program in MatLab to plot : x(t) = cos (t) + j sin (t)
I was told it should be a circle but I'm seeing sinusoidal signal....
Thks in advance.
Mac. Goh

Accepted Answer

Image Analyst
Image Analyst on 25 Oct 2014
Try this
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
t = linspace(0, 2*pi, 90);
j = sqrt(-1);
complexSignal = cos(t) + j*sin (t)
% Get the real component and plot it on the x axis
x = real(complexSignal);
y = imag(complexSignal);
plot(x, y, 'bo-', 'LineWidth', 2);
grid on;
title('Plot of cos(t) + j*sin (t)', 'Fontsize', fontSize);
xlabel('Real Component', 'Fontsize', fontSize);
ylabel('Imaginary Component', 'Fontsize', fontSize);
axis square;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);

More Answers (2)

Star Strider
Star Strider on 25 Oct 2014
Edited: Star Strider on 25 Oct 2014
You have to plot the real parts and imaginary parts:
t = linspace(0,2*pi);
x = @(t) cos (t) + j*sin (t);
figure(1)
plot(real(x(t)), imag(x(t)))
grid
axis equal
xlabel('Re\{x\}')
ylabel('Im\{x\}')

Onimisi
Onimisi on 28 Feb 2023
V=240 % Voltgae across both loads
V = 240
SL1r=120000 % Real Power consumed by load 1
SL1r = 120000
STr=400000 % Total real power consumed
STr = 400000
pf1=0.8 % Power Factor of both Loads
pf1 = 0.8000
pf2= 0.96 % Power of only load 1 leading
pf2 = 0.9600
theta1=acosd(pf1)
theta1 = 36.8699
theta2=acosd(pf2)
theta2 = 16.2602
b=theta1
b = 36.8699
c=theta2
c = 16.2602
j=sqrt(-1)
j = 0.0000 + 1.0000i
complexST=(cosd(b))+(j*sind(b))
complexST = 0.8000 + 0.6000i
complexSL=(cosd(c))+(j*sind(-c))
complexSL = 0.9600 - 0.2800i
ST=(STr/pf1)*complexST
ST = 4.0000e+05 + 3.0000e+05i
SL1=(SL1r/pf2)*complexSL
SL1 = 1.2000e+05 - 3.5000e+04i
SL2=ST-SL1
SL2 = 2.8000e+05 + 3.3500e+05i
  1 Comment
Image Analyst
Image Analyst on 28 Feb 2023
@Onimisi I think you meant to post this as your own question since your post does not seem to be an Answer to @Tiam Huat Goh's 8 year old question.
If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

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