How to 'carry' matrix index with matrix operations

Question

Xiaohan Du 2016-11-15

编辑： Roger Stafford 2016-11-15

Hi all,

I'd like to keep the matrix index while carrying out matrix operations, for example:

a = randi([1 20], 1, 5)';
indx = find(a);
c = [indx a];
b = sort(a);

I obtain:

a = [15 10 2 5 19]'; c = [1 2 3 4 5; 15 10 2 5 19]'; b = [2 5 10 15 19]';

After sort, how can I keep the old correspondence of index and vector in new matrix b? i.e. I want b to be something like this:

b = [3 4 2 1 5; 2 5 10 15 19]';

Thanks!

Answer 1

Roger Stafford 2016-11-15

编辑：Roger Stafford 2016-11-15

Use the second quantity returned by the 'sort' function:

[b,p] = sort(a);

The 'p' is an index for rearranging the first row from 1,2,3,4,5 to 3,4,2,1,5 with indx(p).

Xiaohan Du 2016-11-15

Thanks Roger! I should have checked the function help!