1.4.1. Creating MATLAB variables

MATLAB variables are created with an assignment statement. The syntax of variable assignment is:

variable name = a value (or an expression)

For example,

>> x = expression

where expression is a combination of numerical values, mathematical operators, variables, and function calls. In other words, expression can involve:

• manual entry
• built-in functions
• user-defined functions

In MATLAB, variables are created by using an assignment statement. This is done by setting a variable name to a value or an expression. The expression can be anything from simple numbers to complex calculations involving other variables and functions. For instance, if you want to assign the result of a calculation to a variable named 'x', you would write x = 5 + 2. Here, '5 + 2' is the expression being calculated and assigned to 'x'. This way, you can use 'x' in future calculations.

Think of creating a variable in MATLAB like naming a jar in your kitchen where you store something. When you say x = sugar, it’s like labeling a jar 'sugar' and putting sugar in it. Later, you can easily refer to the 'sugar' jar whenever you need it for a recipe.

Once a variable has been created, it can be reassigned. In addition, if you do not wish to see the intermediate results, you can suppress the numerical output by putting a semicolon (;) at the end of the line. Then the sequence of commands looks like this:

>> t = 5;
>> t = t + 1
>> t = 6

After you create a variable, you can change its value anytime. For example, if you initially set 't' to 5, you can later increase 't' by 1 with the command t = t + 1. If you want to keep your command window tidy and without clutter, you can add a semicolon at the end of any command, which will prevent MATLAB from displaying the result until you explicitly ask to see it.

Imagine you have a box labeled 'snacks'. You initially put 5 snacks in it. Later, you may decide to add 1 more snack. In a MATLAB context, changing the number of snacks in your box (reassigning the variable) represents how reassigning works in programming. The semicolon is like closing the lid of the box temporarily so others don't see how many snacks are inside until you decide to open it again.

If we enter an expression incorrectly, MATLAB will return an error message. For example, if we left out the multiplication sign (*) in the following expression:

>> x = 10;
>> 5x
??? 5x
|
Error: Unexpected MATLAB expression.

When working in MATLAB, it is crucial to use the correct syntax for expressions. If you forget an operator like the multiplication sign (for instance, writing 5x instead of 5*x), MATLAB will generate an error message indicating that it did not understand what you meant. The error helps you identify that there is a problem with how you entered the command, and you must correct it before proceeding.

Consider this like giving someone a recipe but missing crucial steps. If you wrote Bake for 30 minutes instead of Bake for 30 minutes at 350 degrees, the cook might be confused and produce something inedible. Just like in cooking, getting the syntax right in MATLAB is essential for successful outcomes.

To make corrections, we can retake the expressions. But if the expression is lengthy, we make more mistakes by typing a second time. A previously typed command can be recalled with the up-arrow key.

MATLAB allows you to easily access previous commands you have entered so you do not have to type long expressions again. By pressing the up-arrow key, you bring back the last command you typed. This can be useful if you just want to make slight adjustments or corrections without starting from scratch.

Imagine you are writing a long message on your phone. If you made a typo, instead of deleting everything and rewriting the whole message, you can simply scroll back to the message and edit it directly. The up-arrow key in MATLAB performs a similar function by helping you quickly retrieve and modify your earlier commands.

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