# weighted interpolation-error filter 
#
subroutine iner( nf,f, nr,yy,rr, ww, niter, lag, gap1, gapn)
integer i, iter, nf,   nr,           niter, lag, gap1, gapn
real	 f(nf), yy(nr), rr(nr), ww(nr)
temporary real	df(nf), sf(nf), dr(nr), wr(nr), sr(nr)
if( lag < gap1 || lag > gapn )  call erexit('input fails gap1<=lag<=gapn')
do i= 1, nf
	f(i) = 0.
f(lag) = 1.						# set output lag
	call contrunc( 0,0, lag,  nr,yy,  nf,f,  nr,rr)	# make residual
do i= 1,nr
	wr(i) =  rr(i) * ww(i)				# weight residual
call scale( -1.,                                 nr,wr) # negative
do iter= 0, niter {
	do i= 1, nr
		dr(i) =  wr(i) * ww(i)
	call contrunc( 1,0, lag,  nr,yy,  nf,df, nr,dr)	# df=yy*dr
	do i= gap1, gapn
		df(i) = 0.				# constrained lags
	call contrunc( 0,0, lag,  nr,yy,  nf,df, nr,dr)	# dr=yy*df
	do i= 1, nr
		dr(i) =  dr(i) * ww(i)
	call cgstep( iter,  nf,f,df,sf,  nr,wr,dr,sr)	# f=f+df
	}
call contrunc( 0,0, lag, nr,yy,  nf,f,  nr,rr)		# get unweighted resid
return; end