# slide a window around on a wall of data measuring coherency, dip, residual
#
subroutine slider( n1,n2, w1,w2, k1,k2, data, coh, pp, res)
integer	i1,i2,     n1,n2, w1,w2, k1,k2,                    s1,s2, e1,e2
integer	p1,p2				# number of subwindows is p1*p2
real	data(n1,n2)			# input
real	res(n1,n2)			# outputs. math size (n1-1,n2-1)
real	pp(n1,n2), coh(n1,n2)		# outputs defined at pp( 1..p1, 1..p2)
temporary real  count( n1,n2)
temporary real  window(w1,w2), tres(w1,w2)
call null(      count, n1*n2)
call null(        res, n1*n2)
p2=0; e2=w2; while( e2<=n2) {  p2=p2+1; s2=e2-w2+1
p1=1; e1=w1; while( e1<=n1) {  p1=p1+1; s1=e1-w1+1
	do i1 = 1, w1 {
	do i2 = 1, w2 {	window(i1,i2) = data(i1+s1-1,i2+s2-1)
			}}
	call null(                                         tres, w1*w2)
	call puck ( w1, w2, window, coh(p1,p2), pp(p1,p2), tres)
	do i1= s1, e1-1 {
	do i2= s2, e2-1 {
		res(  i1,i2) =    res(i1,i2) + tres( i1-s1+1, i2-s2+1)
		count(i1,i2) =  count(i1,i2) + 1.
		}}
	e1=e1+k1            }
	e2=e2+k2            }
do i2= 1, n2-1 {
do i1= 1, n1-1 {	if( count(i1,i2) > 0. )
				res(i1,i2) = res(i1,i2) / count(i1,i2)
		}}
return; end