! Procedure fitline.nic
! Calculate the coeff (A,B) of the baseline (Ax+B)
! &1 the variable x[npairs]
! &2 the variable y[npairs]
! &3 the respectives weights w[npairs]
! &4 the number of data = npairs
! &5 A
! &6 B
!
define real A1 B1
define integer npts
let npts &4
if npts.gt.1 then
   define real x[npts] y[npts] w[npts]
   let x &1
   let y &2
   let w &3
   define real d sw swx swy swxy swx2
   for i 1 to npts
      let sw   sw+w[i]
      let swx  swx+w[i]*x[i]
      let swy  swy+w[i]*y[i]
      let swxy swxy+w[i]*x[i]*y[i]
      let swx2 swx2+w[i]*x[i]**2
   next
   let d sw*swx2-swx**2
   let A1 (sw*swxy-swx*swy)|d
   let B1 (swy*swx2-swx*swxy)|d
   del /var x y w d sw swx swy swxy swx2
else if npts.eq.1
   let B &2[1]
endif
let &5 A1
let &6 B1
del /var a1 b1 npts