Why is this Simple Octave program failing (NO DEBUGGING, just logical)

Given a set of elements (expressed in a row vector Vi) I extracted the maximum values into another (row) vector (named 'ki') using [ki] = find(Vi==max(max(Vi))). I say values because a lot of numbers repeat. I have to choose randomly between all the repeated values and know the column of the chosen one. For that i made the following code.

ri=rand(1)

for j=1:length(ki)
  if    ((j-1)/length(ki)<ri<=j/length(ki))
    mi=ki(j)
  endif;
endfor  

if (ri==0)
  mi=ki(1)
endif

The problem is that it always gives me mi=ki(last 'j' of the for cycle) (which in this case is mi=ki(length(ki))).

I suspect there must be some elemental logical failure. Forgive my n00bness.

Bye