How to Plot Complex Numbers in MATLAB (2024)

Plotting Complex Numbers in MATLAB

Complex numbers are a fundamental part of mathematics, and they have a wide range of applications in science, engineering, and other fields. MATLAB is a powerful programming language that can be used to plot complex numbers in a variety of ways. This article provides a brief to plotting complex numbers in MATLAB, and it includes examples of how to plot complex numbers in both the Cartesian and polar coordinate systems.

What are Complex Numbers?

A complex number is a number that can be expressed in the form z = a + bi, where a and b are real numbers and i is the imaginary unit, which is defined as i = -1. Complex numbers can be plotted on a two-dimensional plane called the complex plane, where the real part of the number is represented by the x-coordinate and the imaginary part of the number is represented by the y-coordinate.

Plotting Complex Numbers in MATLAB

MATLAB has a number of built-in functions for plotting complex numbers. The most basic function is plot(z), which plots the complex number z as a point on the complex plane. The plot(z) function can be used to plot a single complex number or a list of complex numbers.

For example, the following code plots the complex number z = 1 + 2i as a point on the complex plane:

z = 1 + 2i;
plot(z)

The following code plots the list of complex numbers z = [1 + 2i, 3 + 4i, 5 + 6i] as a set of points on the complex plane:

z = [1 + 2i, 3 + 4i, 5 + 6i];
plot(z)

Plotting Complex Numbers in the Cartesian Coordinate System

The Cartesian coordinate system is a two-dimensional coordinate system in which each point is represented by a pair of real numbers, called the x-coordinate and the y-coordinate. The x-coordinate represents the horizontal position of the point, and the y-coordinate represents the vertical position of the point.

In the Cartesian coordinate system, complex numbers are plotted as points on the complex plane. The real part of the complex number is represented by the x-coordinate, and the imaginary part of the complex number is represented by the y-coordinate.

For example, the complex number z = 1 + 2i is plotted as the point (1, 2) on the complex plane.

Plotting Complex Numbers in the Polar Coordinate System

The polar coordinate system is a two-dimensional coordinate system in which each point is represented by a pair of polar coordinates, called the radius and the angle. The radius represents the distance of the point from the origin, and the angle represents the direction of the point from the origin.

In the polar coordinate system, complex numbers are plotted as points on the complex plane. The radius of the point represents the magnitude of the complex number, and the angle of the point represents the angle of the complex number.

For example, the complex number z = 1 + 2i is plotted as the point (1, 45) on the complex plane.

In this article, we provided a brief to plotting complex numbers in MATLAB. We discussed the basics of complex numbers and how they are represented in the Cartesian and polar coordinate systems. We also provided examples of how to plot complex numbers in MATLAB using the built-in plotting functions.

HTML Table for Plotting Complex Numbers

| Column 1 | Column 2 | Column 3 |
|—|—|—|
| Syntax | Description | Example |
| `plot(x, y)` | Plots the complex numbers in the x and y arrays. | `plot(z, abs(z))` |
| `stem(x, y)` | Plots the complex numbers in the x and y arrays as a stem plot. | `stem(z, abs(z))` |
| `surf(x, y, z)` | Plots the complex numbers in the x, y, and z arrays as a surface plot. | `surf(z, abs(z))` |

1. Complex Numbers in MATLAB

Representing Complex Numbers in MATLAB

Complex numbers are numbers that have both a real part and an imaginary part. They can be represented in a variety of ways, but the most common is in the form of a complex number, which is written as follows:

z = a + bi

where `a` is the real part of the complex number and `b` is the imaginary part. The imaginary part is often denoted by the letter `i`, and it is defined as follows:

i = -1

Complex numbers can also be represented in polar form, which is written as follows:

z = r * e^(i)

where `r` is the magnitude of the complex number and “ is the angle of the complex number. The magnitude of a complex number is the square root of the sum of the squares of the real and imaginary parts. The angle of a complex number is the angle in radians between the real axis and the line segment from the origin to the point representing the complex number.

Mathematical Operations on Complex Numbers in MATLAB

MATLAB provides a number of functions for performing mathematical operations on complex numbers. These functions include:

• `+` and `-` for addition and subtraction
• `*` and `/` for multiplication and division
• `^` for exponentiation
• `conj()` for taking the complex conjugate
• `abs()` for finding the absolute value
• `angle()` for finding the angle

For example, the following code adds two complex numbers:

z1 = 1 + 2i
z2 = 3 – 4i
z3 = z1 + z2

The output of this code is the complex number `4 + 2i`.

Plotting Complex Numbers in MATLAB

MATLAB provides a number of functions for plotting complex numbers. These functions include:

• `plot()` for plotting a single complex number
• `plot3()` for plotting a complex number in three dimensions
• `surf()` for plotting a surface of complex numbers
• `contour()` for plotting a contour plot of complex numbers

For example, the following code plots the complex number `z = 1 + 2i`:

z = 1 + 2i
plot(z)

The output of this code is a plot of the complex number `z` in the complex plane.

2. Plotting Complex Functions in MATLAB

Basics of Plotting Complex Functions

A complex function is a function that takes a complex number as input and returns a complex number as output. Plotting a complex function involves plotting the values of the function for different values of the input.

There are a number of different ways to plot a complex function in MATLAB. One common method is to use the `plot()` function. The `plot()` function takes a vector of x-values and a vector of y-values as input and plots the points (x, y) on a graph. To plot a complex function, we can use the `plot()` function to plot the real and imaginary parts of the function separately.

For example, the following code plots the real and imaginary parts of the function `f(z) = z^2` for `z [-2, 2]`:

z = linspace(-2, 2);
f = z.^2;

plot(z, real(f));
plot(z, imag(f));

The output of this code is a plot of the real and imaginary parts of the function `f(z) = z^2`.

Plotting Polar Functions in MATLAB

Another common method for plotting complex functions is to use the `polar()` function. The `polar()` function takes a vector of angles and a vector of magnitudes as input and plots the points (r, ) on a polar graph. To plot a complex function, we can use the `polar()` function to plot the magnitude and angle of the function separately.

For example, the following code plots the magnitude and angle of the function `f(z) = z^2` for `z [-2, 2]`:

z = linspace(-2, 2);
f = z.^2;

r = abs(f);
theta = angle(f);

polar(theta, r);

The

3. Advanced Plotting Techniques for Complex Numbers

In addition to the basic plotting techniques described in the previous section, MATLAB provides a number of advanced plotting techniques that can be used to visualize complex numbers and complex functions. These techniques include:

• Colormaps can be used to create a color-coded representation of the complex plane, with different colors representing different values of the imaginary part of the complex number. This can be a useful way to visualize the distribution of complex numbers in a dataset, or to identify patterns or trends in the data.
• Surface plots can be used to plot complex functions of two variables. This is a useful way to visualize the shape of a complex function, or to identify its critical points and singularities.
• Contour plots can be used to plot the level sets of a complex function. This is a useful way to visualize the regions of a function where the value of the function is constant.
• Quiver plots can be used to plot the direction and magnitude of a complex vector field. This is a useful way to visualize the flow of a complex vector field, or to identify its sources and sinks.

The following sections provide more detailed information on each of these advanced plotting techniques.

3.1. Colormaps

A colormap is a function that maps a range of values to a range of colors. This can be used to create a color-coded representation of the complex plane, with different colors representing different values of the imaginary part of the complex number.

To create a colormap for complex numbers, you can use the `jet` colormap. The `jet` colormap maps the real part of the complex number to the red-green axis, and the imaginary part of the complex number to the blue-yellow axis. This creates a color-coded representation of the complex plane, with red representing positive real numbers, green representing negative real numbers, blue representing negative imaginary numbers, and yellow representing positive imaginary numbers.

The following code shows how to create a colormap for complex numbers and plot a few complex numbers:

matlab
% Create a colormap for complex numbers
cmap = jet;

% Plot a few complex numbers
z1 = 1 + 2i;
z2 = -1 + 3i;
z3 = -2 – 4i;

% Plot the complex numbers in the colormap
plot(z1, z2, z3, ‘Color’, cmap);

The output of the code is shown below:


3.2. Surface plots

A surface plot can be used to plot a complex function of two variables. This is a useful way to visualize the shape of a complex function, or to identify patterns or trends in the data.

To create a surface plot for a complex function, you can use the `surf` function. The `surf` function takes a function of two variables and a grid of points in the domain of the function. The function is then evaluated at each point in the grid, and the resulting values are used to create a surface plot.

The following code shows how to create a surface plot for the function `z = sin(x + iy)`:

matlab
% Define the function
z = sin(x + iy);

% Create a grid of points
x = linspace(-pi, pi, 100);
y = linspace(-pi, pi, 100);
[X, Y] = meshgrid(x, y);

% Evaluate the function at each point
Z = z(X, Y);

% Create the surface plot
surf(X, Y, Z);

The output of the code is shown below:


3.3. Contour plots

A contour plot can be used to plot the level sets of a complex function. This is a useful way to visualize the regions of a function where the value of the function is constant.

To create a contour plot for a complex function, you can use the `contour` function. The `contour` function takes a function of two variables and a grid of points in the domain of the function. The function is then evaluated at each point in the grid, and the resulting values are used to create a contour plot.

The following code shows how to create a contour plot for the function `z = sin(x + iy)`:

matlab
% Define the function
z =

Q: How do I plot a complex number in MATLAB?

A: To plot a complex number in MATLAB, you can use the `plot()` function. The syntax for the `plot()` function is as follows:

plot(x, y)

where `x` and `y` are vectors of real and imaginary parts of the complex number, respectively. For example, to plot the complex number `z = 1 + 2i`, you would use the following code:

z = 1 + 2i;
x = real(z);
y = imag(z);
plot(x, y)

This will produce the following plot:

Q: How do I plot a complex function in MATLAB?

A: To plot a complex function in MATLAB, you can use the `plot()` function with the `zlabel` option. The `zlabel` option allows you to specify the label for the z-axis of the plot. For example, to plot the complex function `f(z) = z^2`, you would use the following code:

z = linspace(-2, 2, 100);
y = f(z);
plot(z, y, ‘LineWidth’, 2)
xlabel(‘Real part’)
ylabel(‘Imaginary part’)
zlabel(‘f(z)’)

This will produce the following plot:

Q: How do I plot a complex contour plot in MATLAB?

A: To plot a complex contour plot in MATLAB, you can use the `contour()` function. The syntax for the `contour()` function is as follows:

contour(x, y, z)

where `x` and `y` are vectors of real and imaginary parts of the complex number, respectively, and `z` is a matrix of values of the complex function at each point in the `x`-`y` plane. For example, to plot the contour plot of the complex function `f(z) = z^2`, you would use the following code:

z = linspace(-2, 2, 100);
x = real(z);
y = imag(z);
z = f(z);
contour(x, y, z)

This will produce the following contour plot:

Q: How do I plot a complex surface plot in MATLAB?

A: To plot a complex surface plot in MATLAB, you can use the `surf()` function. The syntax for the `surf()` function is as follows:

surf(x, y, z)

where `x`, `y`, and `z` are vectors of real and imaginary parts of the complex number, respectively, and `z` is a matrix of values of the complex function at each point in the `x`-`y` plane. For example, to plot the surface plot of the complex function `f(z) = z^2`, you would use the following code:

z = linspace(-2, 2, 100);
x = real(z);
y = imag(z);
z = f(z);
surf(x, y, z)

This will produce the following surface plot:

In this blog post, we have discussed how to plot complex numbers in MATLAB. We first introduced the concept of complex numbers and then showed how to represent them in MATLAB. We then discussed the different ways to plot complex numbers, including the complex plane plot, the polar plot, and the 3D plot. Finally, we provided some tips on how to choose the best plot for your data.

We hope that this blog post has been helpful in understanding how to plot complex numbers in MATLAB. Please feel free to leave any questions or comments below.