Variables A variable is a named storage location that can be set to a particular value which can be used in subsequent computations. For example, we store a value of 5 in the variable a with the statement a=5. This value remains in a until we store a different value (for example, using the command a=100) or we clear a using the command clear a. Once a variable is set to a particular value, we can get this value by using the variable name in an expression (e.g. a/2). Suppose we wish to compute the circumference of a circle of diameter 5 units using the formula 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

In this command, the product of the value of d (which is known because we earlier set it to 5) and the value of pi (which is a pre defined variable) is computed and the value of the product is stored 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. Variable names are case sensitive, so A and a are different variables. Valid variable names Which of the following are valid variable names? a B ecky_ecky_ecky_ecky_ptang_zoo_boing ecky ecky ecky ecky ptang zoo boing 2nd John-Bigboote Valid. Valid. Valid. Invalid, because the variable name contains spaces. Invalid, because the variable name begins with a number. Invalid, because the variable name contains a dash. There are several predefined variables. The most commonly used include ans - the default variable in which computation results are stored. pi - π. i or j - -1 . Once assigned, variable names remain until they are reassigned or eliminated by the clear command. Variables can contain several types of numerical values. These types include the following: Scalar - a scalar is a single value (i.e. a number). c and d in are scalar variables. Vector - 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 - variables may also contain strings of characters.