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# Variables in MATLAB

Module by: Darryl Morrell. E-mail the author

Summary: This module provides a brief introduction to the use of variables in MATLAB.

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## Variables in MATLAB

A variable in MATLAB is a named value. Using variables allows us to manipulate values symbolically, which is particularly useful when programming.

### Example 1

Suppose we wish to compute the circumference of a circle of diameter 5 units using the formula c = π d c π d . We could first set the variable d to a value of 5:


>> d = 5

d =

5.000


Then we could compute the circumference and assign its value to the variable c:

>> c = pi*d

c =

15.708


To execute this command, MATLAB computes the product of the value of d (which MATLAB knows because we earlier set it to 5) and the value of pi (which is a pre defined variable in MATLAB) and stores the value of the product in the variable c.

Variable names must begin with an upper- or lower-case letter. They may contain letters, digits, and underscores; they may not contain spaces or punctuation characters. MATLAB is case sensitive, so A and a are different variables.

### Exercise 1

#### Valid variable names

Which of the following are valid variable names?

1. a
2. B
3. ecky_ecky_ecky_ecky_ptang_zoo_boing
4. ecky ecky ecky ecky ptang zoo boing
5. 2nd
6. John-Bigboote

#### Solution

1. Valid.
2. Valid.
3. Valid.
4. Invalid, because the variable name contains spaces.
5. Invalid, because the variable name begins with a number.
6. Invalid, because the variable name contains a dash.

MATLAB has several predefined variables. The most commonly used include

• ans - the default variable in which computation results are stored.
• pi - π.
• i or j - -1 -1 .
Once assigned, variable names remain until they are reassigned or eliminated by the clear command.

MATLAB variables can contain several types of numerical values. These types include the following:

• Scalar values - scalar is a mathematical term for a single value (i.e. a number). c and d in Example 1 are scalar variables.
• Vectors - a vector is an ordered series of numbers.
• Matrices - a matrix is a rectangular array of numbers. The ability to do computations on vectors and matrices gives MATLAB its name (MATrix LABoratory).
• strings - MATLAB variables may also contain strings of characters.

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