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MATLAB Basics ARRAY An array is a collection of data values organized into rows and columns and known by a single name.

MATLAB variable names must begin with a letter, followed by any combination of letters, numbers, and the underscore (_) character.

TYPES OF MATLAB VARIABLES The most common types of MATLAB variables are double and char.

Arrays can be classified as either vectors or matrices. Vector is usually used to describe an array with only one dimension, Matrix is usually used to describe an array with two or more dimensions.

Individual elements in an array are addressed by the array name followed by the row and column of the particular element. If the array is a row or column vector, only one subscript is required. For example, in the preceding arrays, a(2,1) is 3 and c(2)is 2. VARIABLE A MATLAB variable is a region of memory containing an array, which is known by a specified name.

Variable of type double A variable of type double is automatically created whenever a numerical value is assigned to a variable name. The numerical values assigned to double variables can be real, imaginary, or complex. For Example var = 10.5 (real value) var = 4i (imaginary value) var = 10 + 10i (complex value) Variables of type char Variables of type char consist of scalars or arrays of 16-bit values, each representing a single character. Arrays of this type are used to hold character strings. They are automatically created whenever a single character or a character string is assigned to a variable name. For example comment = ' This is a character string '

Creating and Initializing Variables in MATLAB MATLAB variables are automatically created when they are initialized. There are three common ways to initialize a variable in MATLAB: 1. Assign data to the variable in an assignment statement. 2. Input data into the variable from the keyboard. 3. Read data from a file. Initializing Variables in Assignment Statements An assignment statement has the general form var = expression; Simple examples of initializing variables with assignment statements include var = 40i; var2 = var/5; array = [1 2 3 4]; x = 1; y = 2;

The number of elements in every row of an array must be the same, and the number of elements in every column must be the same. Attempts to define an array with different numbers of elements in its rows or different numbers of elements in its columns will produce an error when the statement is executed.

For example, if c is not previously defined, the statement C (2,3) = 5; will produce the matrix For example,

Initializing with Shortcut Expressions

What happens when the array contains hundreds or even thousands of elements? It is just not practical to write out each element in the array separately!

Initializing with Built-In Functions

Colon operator The colon operator specifies a whole series of values by specifying the first value in the series, the stepping increment, and the last value in the series. The general form of a colon operator is

first:incr:last For example,

Initializing Variables with Keyboard Input The input function displays a prompt string in the Command Window and then waits for the to type in a response.

For example, consider the following statement:

Transpose operator ( ' )

For example,

Multidimensional Arrays 

MATLAB arrays can have one or more dimensions.

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One-dimensional arrays can be visualized as a series of values laid out in a row or column, with a single subscript used to select the individual array elements.

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Such arrays are useful to describe data that is a function of one independent variable, such as a series of temperature measurements made at fixed intervals of time.

Some types of data are functions of more than one independent variable. Example, We might wish to measure the temperature at five different locations at four different times. In this case, our 20 measurements could logically be grouped into five different columns of four measurements each, with a separate column for each location.

In this case, we will use two subscripts to access a given element in the array:  The first one to select the row  and the second one to select the column. Such arrays are called two-dimensional arrays. MATLAB always allocates array elements in column major order: MATLAB allocates the first column in memory, then the second, and then the third, and so forth, until all of the columns have been allocated.

Subarrays: