c  this file contains subroutine mask and checks
c  
c:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
c  
c  
c  
      subroutine          mask(a,wa,m,error,etype)
c  
c  
c  
c.......................................................................
c  
c  author: Christopher W. Churchill
c
c  history: 15-Aug94   created, CWC
c
c  purpose: create a bad pixel mask for the rejection of bad grid 
c           points from the fit
c           
c           
c  input:   reject   = sigma rejection factor
c           Imin     = 2D grid to fit [e-] at xmin locations
c           sig      = Imin uncertainty ; fitting weights
c           xmin     = interorder map [pixel locations]
c           gain     = instrumental gain [e-/DN]
c           a        = fitting coefficients
c           wa       = working array for fit residuals
c           error    = (logical) error flag
c           etype    = error type
c
c  output:  sig      = sigma set to 0. if rejected pixel 
c
c  I/O: none
c
c  options: none
c
c  routines called: linlsf
c
c  description: this routine fits a polynomial of order yorder to
c               each interorder array Imin ; pixel locations with
c               fit residuals greater the reject times the fiting
c               sigma have their sigma set to zero ; the zero
c               sigma serve as flags for exclusion from the LSF
c
c  NB: it would be very nice if this was iterative rejection 
c      and the process be made interactive like icfit
c
c.......................................................................
c
      implicit undefined  (a-z)
      logical             error
      integer             j,icol,m,etype
      double precision    chisq,fitsig,fsigma,a(1),wa(1)
      include             'hamscatt.par'
      include             'hamscatt.com'
c  
c  
c  
c
c  
c
c  loop over interorders
      do 11 j=1,ndata
c
c  fit the interorder data to a yorder polynomial
c  on return, wa contains the fit residuals
c  on error, j is the error type
       call linlsf(j,a,wa,chisq,fitsig,error,2)   
       if (error) then
        etype = j
        return
      end if
c  
c  loop over columns to flag rejects ; decrement the merit 
c  function vector length, m 
       do 10 icol=1,ncols
        fsigma = wa(icol)/fitsig
        if (abs(fsigma).gt.reject) then
         sig(j,icol) = 0.
         m = m - 1
        end if
 10    continue
c  
c  next interorder
 11   continue
c  
      return
      end
c  
c.......................................................................
c
c:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
c  
c  
c  
      subroutine          checks(n,m,tol,error,ecode)
c  
c  
c  
c.......................................................................
c  
c  author: Christopher W. Churchill
c
c  history: 15-Aug94   created, CWC
c
c  purpose: create a bad pixel mask for the rejection of bad grid 
c           points from the fit
c           
c           
c  input:   norders  = number of orders in image
c           toler    = input tolerance common variable
c           ncols    = number of columns in image
c           gamma    = profile power law
c           nvec     = max vector length of merit function
c
c  output:  n        = sigma set to 0. if rejected pixel 
c           m        = working length of merit function
c           tol      = tolerance parameter
c           error    = (logical) error flag
c           ecode    = type of error
c           termflag = (logical) high=global+local ; low=global
c
c  I/O: none
c
c  options: none
c
c  routines called: none
c
c  description: see subroutine comments
c
c.......................................................................
c
      implicit undefined  (a-z)
      logical             error
      integer             n,m,ecode
      double precision    tol
      include             'hamscatt.par'
      include             'hamscatt.com'
c
c
c
c
c
c  define the parameters tol, ndata, and m
c  it is advertised that the edges of the chip are fit, 
c  this is not so (yet), so ndata is less than norders
      tol   = toler
      ndata = norders - 1
      m     = ncols*ndata
c
c  define n based upon gamma
c  gamma=0 means repress the local term
      if (gamma.eq.0.d0) then
       termflag = .false.
       n = xorder*yorder
      else
       termflag = .true.
       n = xorder*yorder + 1
      end if

c  be sure that we have not exceeded work space limtations
      if (m.gt.nvec) then
       error = .true.
       ecode = 1
      end if
      if (n.gt.nn) then 
       error = .true.
       ecode = 2
      end if
c
c
      return
      end
c      
c.......................................................................
c..eof