How to Plot a Unit Step Function in Matlab

Introduction to Matlab Unit Step Function

MATLAB unit step function is used to enable representation of a signal or pulse without the need to specify separate functional forms for various ranges of time. The unit step function is used to test the low and high-frequency response of any system in a single attempt. The unit step function takes theoretically zero time to change from 0 to 1. The unit step function is commonly called a Heaviside function.

Syntax:

H = Heaviside (t)

Details of unit step or Heaviside function:

1. H = heaviside (t) is used to evaluate the unit step function value at 't'
2. It is discontinuous in nature and returns following values:
   1. 0 if t < 0
   2. 1/2 if t = 0
   3. 1 if t > 0

Let us now understand how to use a Heaviside function or unit step function in MATLAB. We will discuss the code to do the following:

1. The use of the Heaviside function
2. Plotting a Heaviside function

Please note that we will use a symbolic object as the input in the below examples. However, if we use a floating-point input, we will get a floating-point output. Since the output for t < 0 and t > 0 will be an integer, it will not make a difference. We can see the difference when input is t = 0 (refer to Example 3).

Examples of Matlab Unit Step Function

Let us discuss some examples of Matlab Unit Step Function:

Example #1

In this example, we will use the unit step function for input less than 1 and will see the output.

Code:

H = heaviside (sym (-10))

[Initializing the symbolic object and passing a negative number as an argument]

This is how our input and output will look like in MATLAB:

Input:

Output:

As we can see, we have obtained 0 as the output for an argument which is a negative number, i.e. when 't' is less than 0.

Example #2

In this example, we will use the unit step function for an input greater than zero.

Code:

H = heaviside (sym (20))

[Initializing the symbolic object and passing a positive number as an argument]

This is how our input and output will look like in MATLAB:

Input:

Output:

As we can see, we have obtained 1 as the output for an argument that is a positive number, i.e. when 't' is greater than 0.

Example #3

This example will use the unit step function for an input greater than equal to zero. Here, we will discuss 2 scenarios:

1. Using a symbolic object
2. Not using a symbolic object (Using a floating-point input)

Code when using a symbolic object:

A = heaviside (sym (0))

[Initializing the symbolic object and passing zero as an argument]

This is how our input and output will look like in MATLAB:

Input:

Output:

As we can see, we have obtained 1/2 as the output for an argument equal to zero.

Code without using a symbolic object (Using floating-point input):

H = heaviside (0)

[Passing zero as an argument to 'heaviside' function]

This is how our input and output will look like in MATLAB:

Input:

Output:

As we can see, we have obtained a floating-point when we have not used a symbolic object in the input.

Next, we will learn to plot the unit step function in MATLAB.

Example #4

In this example, we will plot the unit step function for values between 0 and 5. As we know, the unit step function gives 0.5 as output for t = 0 and 1 for t > 0, so for the values between 0 and 5, the output will be starting from 0.5 (for t = 0), and then it will be 1 for all the values above 0.

Code;

syms t

[Initializing the symbolic object]

fplot (heaviside (t), [0, 5])

[Using 'fplot' function to plot the 'heaviside' function with values between 0 and 5]

This is how our input and output will look like in MATLAB:

Input:

Output:

As we can see in the output, for the values between 0 and 5, the output is starting from 0.5 (for t = 0), and then it is 1 for all the values above 0.

Example #5

In this example, we will plot the unit step function for values between -5 and 5. As we know, the unit step function gives 0 as output for t < 0, 1 for t > 0 and 0.5 for t = 0, so for the values between -5 and 5, the output will be starting from 0 (for t < 0) and then it will be 0.5 for t = 0 and finally 1 for all the values above 0.

Code:

syms t

[Initializing the symbolic object]

fplot (heaviside (t), [-5, 5])

[Using 'fplot' function to plot the 'heaviside' function with values between -5 and 5]

This is how our input and output will look like in MATLAB:

Input:

Output:

As we can see in the output, for the values between -5 and 0, the output is 0, and then there is a unit step from 0 to 1 when the input values are in the range of 0 to 5

Conclusion

The unit step function changes from 0 to 1 in almost no time. It can take three values: 0, 1, and ½. It is commonly used to test the low and high-frequency response of any system in a single attempt.

Recommended Articles

This is a guide to Matlab Unit Step Function. Here we discuss the Introduction, syntax, and examples. You may also have a look at the following articles to learn more –

1.  Nyquist Matlab
2. Matlab limit
3. Matlab Saveas
4. Matlab Cell

How to Plot a Unit Step Function in Matlab

Source: https://www.educba.com/matlab-unit-step-function/

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