/* VERTWT.C: returns a probability weight for each vertex of the hypercube
 *           containing a point to be interpolated such that the weighted
 *           average (expectation) of the vertices equals the point to be
 *           interpolated. Used in interpolate.c and interp.c
 *           
 *   Input vectors:
 *
 *         indx: a dx1 vector of indices (i1,i2,...,id) where ij is 0 or 1,
 *               with 0 being the lower bound in dimension j, and 1 being the
 *               upper bound in that dimension
 *
 *         wts:  a dx1 vector if wts (w1,w2,...,wd) each in the unit interval
 *               such that if xj is the jth coordinate of the point x to be
 *               interpolated, then xj=wj*ubnd(j)+(1-wj)*lbnd(j), where 
 *               lbnd(j) is the smaller value of the jth component of the
 *               hypercube containing x and ubnd(j) is the larger value of the
 *               hypercube containing x, i.e.
 *
 *                   lbnd(j) <= xj <= ubnd(j),   j=1,...,d
 *
 *
 *    John Rust, University of Maryland, June 2005 */

double vertwt(double *wts,int *indx,int d)
{
  
  double wt;
  int i;

  wt=1.0;

  for (i=0; i<d; i++)
  {
     if (indx[i])
     {
        wt=wt*wts[i];
     }
     else 
     {
        wt=wt*(1.0-wts[i]);
     }
  }

  return wt;
}