T Y VECTOR WHICH CORRESPONDS TO THE POSITION OF THE</span>
<span class="c">!     GIVEN ELEMENT OF INTEREST IN THE ORIGINAL X VECTOR.</span>
<span class="c">!     THE CODE IS LENGTHENED FROM THIS BASIC ALGORITHM</span>
<span class="c">!     BY A SECTION WHICH CUTS DOWN THE SEARCH IN THE XS VECTOR,</span>
<span class="c">!     AND BY A SECTION WHICH OBVIATES (UNDER CERTAIN CIRCUMSTANCES)</span>
<span class="c">!     THE NEED FOR RECALCULATING THE RANK OF AN ELEMENT IN XS.</span>
<span class="c">!</span>
<span