Illustration of Indexing:

Though, rather than of creating the index vector manually as shown here, the process to initialize the index vector is use to a sort function. The algorithm is as shown below:

•  Initialize the values in index vector to be the indices 1,2, 3, ....
•  Use any of the sort algorithm, but compare the elements in the original vector by using the index vector to index into it (example, using grades (grade_index(i))).
•  Whenever the sort algorithm calls for replacing values, replace the elements in the index vector, not in the original vector.

The function which implements this algorithm is as shown below:

For illustration, for the grades vector as given:

>> clear grade_index

>> grade_index = createind(grades)

grade_index =

2 5 1 6 4 3

>> grades(grade_index)

ans =

70 80 85 91 95 100