t vector X remains unaltered.</p>
<p>Due to conflicting use of labeled common /block2_real64/ by this
   rank subroutine and the SPCORR (Spearman rank correlation coefficient)
   subroutine, the vector XS of this rank subroutine has been placed in
   labeled common /block4_real64/</p>
<p>The first and third arguments in the calling sequence may be identical;
   that is, an &lsquo;in place&rsquo; ranking is permitted. The calling sequence
   call RANK(X,N,X) is valid, if desired.</p>
<p>The sorting algorthm 