PRO ucles_resample, nw, w, fn,fs, wb,wi


  ; Procedure to resample a 2d echelle frame onto a uniform wavelength scale

  ; Input
  ; w    nw x no  wavelengths
  ; fn   nw x no  normalized fluxes
  ; fs   nw x no  rectification function

  ; Output
  ; wb   nw x no  wavelengths remapped to constant dx
  ; wi        no  vector containing number of wavelengths in each order
  ; fn   nw x no  normalized fluxes remapped to wb
  ; fs   nw x no  rectification function remapped to wb



  ; resample all data onto uniform wavelength grid
  ; nb the smoothing fucntion must also be resampled


  PRINT,'UCLES_RESAMPLE: resample echelle spectrum'

  no = n_elements(w)/nw

  wb = w
  wi = intarr(no)
  
  dwx = (wb(nw-1,*)-wb(0,*)) / (nw-1)
  dw = max ( dwx )
  w0 = wb(0,0)
  PRINT,'uniform grid, dw =',dw


  FOR j = 0,no-1 DO BEGIN
    wl = w0 +  floor ( (wb(   0,j)-w0)/dw ) * dw 
    wu = w0 +  floor ( (wb(nw-1,j)-w0)/dw ) * dw 

    tw = wb(*,j) & tf = fn(*,j)
    resample,tw,tf,wl,wu,dw

    tw = wb(*,j) & ts = fs(*,j)
    resample,tw,ts,wl,wu,dw

    tn = n_elements(tw)-2
    wb(0:tn,j) = tw(0:tn) & fn(0:tn,j) = tf(0:tn) & fs(0:tn,j) = ts(0:tn) 
    fs(tn+1:nw-1,j) = 0.
    wi(j) = tn
  ENDFOR

  ; remove high frequency noise introduced by resample
  FOR j = 0,no-1 DO BEGIN
    tn=wi(j)
    fs(0:tn,j) = qqsm ( w(0:tn,j),fs(0:tn,j),1.0 )
  ENDFOR 

  window,1
    shade_surf,fs,zrange=[0,max(fs)]

END