MATLAB(R) by Example (eBook)

Objectives

Topics

2.1.1.1 Using Matlab Special Variables

In Matlab, every variable created should have a value. Variables are created either by Matlab or by the user. Variables created by Matlab are considered to be special variables, whose values are assigned by Matlab. For example, the special variable pi (π), whose value is approximated here to 3.1416. To find the value of the special variable pi, type at the Command Prompt

Then press Enter. Matlab responds with

This command generates another special variable ans and assigns the value 3.1416 to it. The special variable ans saves the result of any Matlab operation if the value of the result is not specifically assigned to a variable. For example, type at the Command Prompt

Then press Enter. Matlab responds with

Other examples of special variables are i and j. The value for both variables is defined as Normally, mathematicians use the term i to represent whereas engineers use the term j to represent the same thing.

To find the value of the special variable i, type at the Command Prompt

Then press Enter. Matlab responds with

To get some help about the variable i, type at the Command Prompt

Then press Enter. Matlab responds and gives you some information about the special variable i as follows.

To find the value of the special variable j, type at the Command Prompt

Then press Enter. Matlab responds with

2.1.1.2 Changing the Values of Matlab Special Variables

The user can change the value of the special variables. For example, type at the Command Prompt

Then press Enter. Matlab responds with

Now the value for the special variable pi has been changed to 1.

To restore the value of the special variable pi, type at the Command Prompt

Then press Enter.

To display the value of the variable pi, type at the Command Prompt

Then press Enter. Matlab responds with

2.1.2.1 Naming a User-Defined Variable

The user can also create Matlab variables and assign values to the created variables. The variable name should satisfy the following requirements:

The following variable names are acceptable

The following names are not suitable to be used as variable names:

Matlab responds by displaying some information about the sum function.

2.1.2.2 Matlab is Case Sensitive

Matlab is a case-sensitive programming language as it distinguishes lowercase from uppercase. The variable name x is considered to be different from the variable name X, which can lead to confusion, so be careful! For example, type at the Command Prompt

Then Press Enter. Matlab responds by creating the variable x and assigning the value “1” to it.

To display the content of the x variable, type at the Command Prompt

Then Press Enter. Matlab responds by displaying the value of the variable x as

To find the value of X, type at the Command Prompt

Then Press Enter. Matlab gives the results

In Matlab, the variable x is different from the variable X. Matlab is case sensitive. For example, cost, Cost and COST are viewed as being three different variables in Matlab.

2.1.2.3 Clearing a User-Defined Variable

Create a variable y

To display the content of y, type at the Command Prompt

Then Press Enter. Matlab responds by displaying the value of y as

To clear the variable y, type at the Command Prompt

Then Press Enter. To be sure that the variable y is cleared, type at the Command Prompt

Then Press Enter. Matlab responds with

Objectives

Topics

2.2.1.1 round Function

This function rounds a real number upward, or downward, toward the nearest integer. The operation of this function is best explained by way of examples. Type at the Command Prompt

Then press Enter. Matlab responds with

A second example, type at the Command Prompt

Then press Enter. Matlab responds with

2.2.1.2 fix Function

This function truncates (eliminates) the decimal part of a real number, leaving the integer part unchanged. The operation of this function is best explained by way of examples. Type at the Command Prompt

Then press Enter. Matlab responds with

A second example, type at the Command Prompt

Then press Enter. Matlab responds with

2.2.1.3...