Not much of your code makes sense. The row vector u is defined like this (so far no problems):
u = [ 0.01 9.8e-04 6.4e-05 ];
but then you use indexing to take only the second column, which is a scalar:
>> u(:,2)
ans = 0.00098000
You then sort that scalar, where obviously the sort index of a scalar is one (and it makes absolutely no difference using 'ascend' or 'descend'), and this is easy to confirm:
>> [~,idx] = sort(u(:,2))
idx = 1
You then use the index 1 to select the first row of u. I guess you thought that your code did some sorting and that idx would change the order. In fact your code is simply equivalent to:
sortedu = u(1,:)
which because u is a row vector anyway is simply
sortedu = u
This is not the output that you showed us, which means that you did not actually give us the data and/or code that you used. If you do not show us what you are actually doing, then you make it hard for us to help you.
My suspicion is that you actually have a string array, not a numeric array as you showed us.
