let/quiet Xi = $1
   let/quiet Yi = $2
   let/quiet mX = Xi[l=@ave]
   let/quiet mY = Yi[l=@ave]
   let/quiet nX = Xi[l=@NGD]
   let/quiet xidt = xi - Xi[l=@ave]
   let/quiet yidt = yi - Yi[l=@ave]
!
   let/quiet XiYi = Xidt*Yidt
   let/quiet sXiYi = XiYi[l=@sum]/nx
!
   let/quiet sXidt = Xidt[l=@sum]
   let/quiet sYidt = Yidt[l=@sum]
!
   let/quiet Xidt2 = Xidt * Xidt
   let/quiet Yidt2 = Yidt * Yidt
!
   let/quiet sdx = (Xidt2[l=@sum]/nx)^0.5
   let/quiet sdy = (Yidt2[l=@sum]/nx)^0.5
!
   let/quiet rxy = sxiyi/sdx/sdy
!
   list rXY