function interp_2pt,x,y,y2,miss

;------------------------------------------------------------------
;
; Do a 2 point linear interpolation of x,  from the y grid to the 
; y2 point (or grid) 
;
; input:
;   x......x axis variables 
;   y......y axis variables 
;   y2.....interpolate to this value or grid
;   miss...missing data value
;
; output:
;   result...the data value from x at y2
;
; source: Mark Hervig 
;------------------------------------------------------------------

  if (n_elements(x) ne n_elements(y)) then begin
    print,'x and y arrays are not the same size in interp_2pt.pro!!!'
    stop
  endif

  n  = n_elements(y)
  n2 = n_elements(y2)
  x2 = fltarr(n2) + miss

  ok = where(x ne miss,nok)

  if (nok gt 1) then begin

    xa = x(ok)
    ya = y(ok)

    for i = 0,n2-1 do begin

      for j = 0,nok-2 do begin

        if (ya(j) ge y2(i) and ya(j+1) le y2(i)) then begin
          term  = (y2(i)-ya(j)) / (ya(j+1)-ya(j))
          x2(i) = term * (xa(j+1)-xa(j)) + xa(j)
          goto,jump1
        endif
        if (ya(j) le y2(i) and ya(j+1) ge y2(i))then begin
          term  = (y2(i)-ya(j)) / (ya(j+1)-ya(j))
          x2(i) = term * (xa(j+1)-xa(j)) + xa(j)
          goto,jump1
        endif

      endfor

      jump1:
    endfor

  endif

  return,x2
  end