; ----------------------------------------------------------------------
; Compute highest weighted deviation and index number.
; Also return:
;     'yrms'   (RMS of Y values from median of Y values (ww>0), excluding 20% worse values ).
;     'devmed' (median of deviations from fit (ww>0) ).
;     'devrms' (RMS of deviations from fit (ww>0), excluding 20% worse values ).
;     'hidev'  (high deviation from fit (ww>0) ).
;
pro nsx_hidevrms, nn, xx, yy, ww, order, xoff, coef, yrms, devmed, devrms, hidev, hiii

  devarr = dblarr(3000)
  arr = dblarr(3000)
  
; Y values: Median and rms.
  narr=0                         
  for ii=0,nn-1 do begin
     if (ww[ii] gt 0.) then begin
        arr[narr] = yy[ii] 
        ++narr 
     endif
  endfor
  ymedian = cfind_median8(narr,arr) 

; Y values: Compute RMS excluding the 20% largest deviations. */
  for ii=0,narr-1 do devarr[ii] = ABS((arr[ii] - ymedian)) 
  cqcksrt8,narr,devarr
  narr80 = cnint( 0.8 * double(narr) ) 
  sum = 0. 
  for ii=0L, narr80-1 do sum = sum + (devarr[ii] * devarr[ii]) 
  yrms = sqrt(( sum / double(narr80) )) 

; Fit deviations: compute RMS relative to fit excluding 20% largest deviations. 
  narr=0 
  for ii=0,nn-1 do begin
     if (ww[ii] gt 0.) then begin
        ff = cpolyval(order+1,coef,(xx[ii]-xoff)) 
        devarr[narr] = ABS(( yy[ii] - ff )) 
        ++narr 
     endif
  endfor
  devmed = cfind_median8(narr,devarr) 
  narr80 = cnint( 0.8 * double(narr) ) 
  sum = 0. 
  for ii=0,narr80-1 do sum = sum + (devarr[ii] * devarr[ii]) 
  devrms = sqrt(( sum / double(narr80) )) 

; Highest deviation. */
  hidev=-1.
  hiii=-1  
  for ii=0,nn-1 do begin
     if (ww[ii] gt 0.) then begin
        ff = cpolyval(order+1,coef,(xx[ii]-xoff)) 
        dev = ABS(( yy[ii] - ff )) 
        if (dev gt hidev) then begin
           hidev=dev
           hiii=ii
        endif
     endif
  endfor
  
end