Look at this example:
>> x = [1, 4, 2, 5, 3, 7, 6] ; % Fake x and y.
>> y = x + 10 ;
>> for k = 1 : 7, y(x == k), end
ans =
11
ans =
12
ans =
13
ans =
14
ans =
15
ans =
16
ans =
17
Here, we use logical indexing to extract the relevant element of y, as illustrated below for finding the y corresponding to x equals 5:
>> x == 5
ans =
0 0 0 1 0 0 0
>> class(x)
ans =
double
The test of equality (relational operator) returns a vector of logicals that whose elements indicate whether the test is true (1) or false (0). This vector can be used for indexing y (look at logical indexing in the doc if needed):
>> y(x == 5)
ans =
15
