pro removegrad1,x,f,nf,mask
; IDL Version 3.0.0 (sunos sparc)
; Journal File for schou@skaelv.Stanford.EDU
; Working directory: /home0/schou/lnu
; Date: Thu Sep 30 17:13:22 1993
 
a=fltarr(nf,nf)
b=fltarr(nf)
for i=0,nf-1 do begin
  b(i)=total(mask*x*f(*,*,i))
  for j=i,nf-1 do begin
    a(i,j)=total(mask*f(*,*,i)*f(*,*,j))
    a(j,i)=a(i,j)
  end
end
ludcmp,a,indx,d
lubksb,a,indx,b
for i=0,nf-1 do x=x-b(i)*f(*,*,i)

end