ドキュメンテーション

Accessing Array Elements

This example shows how to access selected elements of an array using indexing.

Create a magic square matrix constructed from the integers 1 through 16 with equal row and column sums.

disp('Create 4-by-4 magic square a:')
disp('>> a = magic(4)')
a = magic(4)
Create 4-by-4 magic square a:
>> a = magic(4)

a =

16     2     3    13
5    11    10     8
9     7     6    12
4    14    15     1

To reference a particular element in an array, specify its row and column number using the following syntax, where A is the matrix variable. Always specify the row first and column second.

disp('Reference element in row 4, column 2:')
disp('>> a(4, 2)')
a(4, 2)
Reference element in row 4, column 2:
>> a(4, 2)

ans =

14

To refer to multiple elements of an array, use the colon ':' operator, which allows you to specify a range of elements using the form 'start:end'.

disp('List the elements in the first three rows and the second column of a:')
disp('>> a(1:3, 2)')
a(1:3, 2)
List the elements in the first three rows and the second column of a:
>> a(1:3, 2)

ans =

2
11
7

The colon alone, without start or end values, specifies all the elements in that dimension.

disp('Select all the columns in the third row of a:')
disp('>> a(3, :)')
a(3, :)
Select all the columns in the third row of a:
>> a(3, :)

ans =

9     7     6    12