FUNCTION dustem_compute_stokes,p_dim,stp,dustem_qsed=dustem_qsed,dustem_used=dustem_used,Q_spec=Q_spec,U_spec=U_spec,out_st=out_st,_extra=extra

;+
; NAME:
;    dustem_compute_stokes
; PURPOSE:
;    Provides Stokes Q and Stokes U dustem spectra and wrapper SEDs 
; CATEGORY:
;    Dustem
; CALLING SEQUENCE:
;    out=dustem_compute_polsed(p_dim[,st=][,_extra=][,/help])
; INPUTS:
;    p_dim      = parameter values
; OPTIONAL INPUT PARAMETERS:
;    stp        = Dustem structure
; OUTPUTS:
;    sed         : computed SED for filters in !dustem_data
;    dustem_qsed : SED in Q
;    dustem_used : SED in U
; OPTIONAL OUTPUT PARAMETERS:
;    stp        = Dustem output structure
; ACCEPTED KEY-WORDS:
;    help      = If set, print this help
; COMMON BLOCKS:
;    None
; SIDE EFFECTS:
;    None
; RESTRICTIONS:
;    The dustem idl wrapper must be installed
; PROCEDURE:
;    None
; EXAMPLES
;    
; MODIFICATION HISTORY:
;    Written by J.-Ph. Bernard
;    see evolution details on the dustem cvs maintained at CESR
;    Contact J.-Ph. Bernard (Jean-Philippe.Bernard@cesr.fr) in case of problems.

IF keyword_set(help) THEN BEGIN
    doc_library,'dustem_compute_stokes'
    out=0.
    goto,the_end
ENDIF

IF not keyword_set(stp) THEN BEGIN
    stp=dustem_run(p_dim)
    dustem_activate_plugins,p_dim/(*(*!dustem_fit).param_init_values),stp
ENDIF


If keyword_set(result) THEN result=stp

fact = 1.e4*1.E20/(4.*!pi)/(3.e8/1.e-6/(stp.polsed).wav)*1.e20/1.e7
stI = stp.sed.em_tot * fact   ;This is Total intensity I
P = stp.polsed.em_tot * fact   ;This is Polarized intensity P
out=0.
Nwaves=(size(stI))[1]

frac=P/stI
tes=where(finite(frac) eq 0)
frac(tes)=0.

;if Q and U have already been computed elsewhere
FOR i=0L,n_tags(*!dustem_scope)-1 DO BEGIN   
    
    IF total(strsplit((*(*!dustem_scope).(i)),'+',/extract) EQ 'MODIFY_DUST_POLAR_ANGLE') THEN BEGIN
        
        Q_spec=(*(*!dustem_plugin).(i))[*,0]
        U_spec=(*(*!dustem_plugin).(i))[*,1]
        
    ENDIF 
ENDFOR    


FOR i=0L,n_tags(*!dustem_scope)-1 DO BEGIN   
    
    IF total(strsplit((*(*!dustem_scope).(i)),'+',/extract) EQ 'REPLACE_QSED') THEN BEGIN
        
        Q_spec=(*(*!dustem_plugin).(i))[*,1]
    ENDIF 
    
    IF total(strsplit((*(*!dustem_scope).(i)),'+',/extract) EQ 'REPLACE_USED') THEN BEGIN
        U_spec=(*(*!dustem_plugin).(i))[*,2]
    ENDIF
    
ENDFOR    


    
IF ~isa(Q_spec) && ~isa(U_spec) THEN polar_ippsi2iqu,stI,Q_spec,U_spec,frac,replicate(0.,Nwaves) 
        
FOR i=0L,n_tags(*!dustem_scope)-1 DO BEGIN
    
    IF total(strsplit((*(*!dustem_scope).(i)),'+',/extract) EQ 'ADD_QSED') THEN BEGIN
        Q_spec+=(*(*!dustem_plugin).(i))[*,1]
    ENDIF
    
    IF total(strsplit((*(*!dustem_scope).(i)),'+',/extract) EQ 'ADD_USED') THEN BEGIN
        U_spec+=(*(*!dustem_plugin).(i))[*,2]
    ENDIF              
    
ENDFOR


;-----------------------------------------

;largeP=sqrt(StokesQ^2+StokesU^2)

;INITIALIZING THE STOKES SEDS
dustem_qsed = (*!dustem_data.sed).values * 0.
dustem_used = dustem_qsed


if not isarray(stI) THEN stop 


;Performing color corrections on the dustem spectra and generating the SEDs at the given filters 

IF !dustem_do_cc NE 0 AND !dustem_never_do_cc EQ 0 THEN BEGIN
    message,'DOING color correction calculations',/info
ENDIF ELSE BEGIN
          message,'SKIPPING color correction calculations',/info
      ENDELSE

ind_polsed=where((*!dustem_data.polsed).filt_names NE 'SPECTRUM',count_polsed)
  
IF count_polsed NE 0 THEN BEGIN ; INCLUDE COLOR CORRECTIONS OF (Q,U) for dust & synch
  filter_names=((*!dustem_data.polsed).filt_names)(ind_polsed)
      
  if isa(dustem_qsed) then begin 
    sqsed=dustem_cc(stp.sed.wav,Q_spec,filter_names,cc=cc)
    dustem_qsed(ind_polsed)=sqsed
  endif
  if isa(dustem_used) then begin
    sused=dustem_cc(stp.sed.wav,U_spec,filter_names,cc=cc)
    dustem_used(ind_polsed)=sused
  endif
  ;--------------------------------------------------------------------------
  
ENDIF

;For spectrum data points, interpolate in log-log
;Linear interpolation leads to wrong values, in particular where few
;wavelengths points exist in the model (long wavelengths).


ind_spec=where((*!dustem_data.polsed).filt_names EQ 'SPECTRUM',count_spec)
IF count_spec NE 0 THEN BEGIN
  if isa(dustem_qsed) then dustem_qsed(ind_spec)=interpol(Q_spec,stp.wav,(((*!dustem_data.polsed).wav)(ind_spec)))  
  if isa(dustem_used) then dustem_used(ind_spec)=interpol(U_spec,stp.wav,(((*!dustem_data.polsed).wav)(ind_spec)))
ENDIF
out_st=stp


;clean pointers
heap_gc

the_end:

RETURN,out

END