3
7
1
The result is a column vector of the elements in A that are less than 9. Since B is a logical matrix, this
operation is called logical indexing. In this case, the logical array being used as an index is the
same size as the other array, but this is not a requirement. For more information, see “Array
Indexing”.
Some problems require information about the locations of the array elements that meet a condition
rather than their actual values. In this example, you can use the find function to locate all of the
elements in A less than 9.
I = find(A < 9)
I = 8×1
3
6
7
11
14
16
17
22
The result is a column vector of linear indices. Each index describes the location of an element in A
that is less than 9, so in practice A(I) returns the same result as A(B). The difference is that A(B)
uses logical indexing, whereas A(I) uses linear indexing.
Apply Multiple Conditions
You can use the logical and, or, and not operators to apply any number of conditions to an array; the
number of conditions is not limited to one or two.
First, use the logical and operator, denoted &, to specify two conditions: the elements must be less
than 9 and greater than 2. Specify the conditions as a logical index to view the elements that
satisfy both conditions.
A(A<9 & A>2)
ans = 5×1
5
3
8
3
7
The result is a list of the elements in A that satisfy both conditions. Be sure to specify each condition
with a separate statement connected by a logical operator. For example, you cannot specify the
conditions above by A(2
Find Array Elements That Meet a Condition
5-3
7
1
The result is a column vector of the elements in A that are less than 9. Since B is a logical matrix, this
operation is called logical indexing. In this case, the logical array being used as an index is the
same size as the other array, but this is not a requirement. For more information, see “Array
Indexing”.
Some problems require information about the locations of the array elements that meet a condition
rather than their actual values. In this example, you can use the find function to locate all of the
elements in A less than 9.
I = find(A < 9)
I = 8×1
3
6
7
11
14
16
17
22
The result is a column vector of linear indices. Each index describes the location of an element in A
that is less than 9, so in practice A(I) returns the same result as A(B). The difference is that A(B)
uses logical indexing, whereas A(I) uses linear indexing.
Apply Multiple Conditions
You can use the logical and, or, and not operators to apply any number of conditions to an array; the
number of conditions is not limited to one or two.
First, use the logical and operator, denoted &, to specify two conditions: the elements must be less
than 9 and greater than 2. Specify the conditions as a logical index to view the elements that
satisfy both conditions.
A(A<9 & A>2)
ans = 5×1
5
3
8
3
7
The result is a list of the elements in A that satisfy both conditions. Be sure to specify each condition
with a separate statement connected by a logical operator. For example, you cannot specify the
conditions above by A(2
Find Array Elements That Meet a Condition
5-3