#$=head1 NAME
#$
#$createnhelix - create non stationary helix filter
#$
#$
#$=head1 SYNOPSIS
#$
#$C<aa=createnhelix(nd,center,gap,na,patch)>
#$
#$=head1 INPUT PARAMETERS
#$
#$=over 4
#$
#$=item nd      - C<integer(:)> 
#$
#$      size of data
#$
#$=item center  - C<integer(:)> 
#$
#$      location of the 1 of the filter within na box
#$
#$=item gap     - C<integer(:)> 
#$
#$      distance along each axis before filter coef
#$
#$=item na      - C<integer(:)> 
#$
#$      size of box arround filter
#$
#$=item patch   - C<integer(:)> 
#$
#$      what model point a given filter will act on
#$
#$=back
#$
#$=head1 RETURN VALUE
#$
#$=over 4
#$
#$=item aa       - C<type(nfilter)> 
#$
#$      Helix filter
#$
#$=back
#$
#$=head1 DESCRIPTION
#$
#$Create a non-stationary helix filter
#$
#$=head1 SEE ALSO
#$
#$L<createhelix>,L<nhelix>,L<createmshelix>
#$
#$=head1 LIBRARY
#$
#$B<geef90>
#$
#$=cut
module createnhelixmod {      # Create non-stationary helix filter lags and mis
use createhelixmod
use nhelix
use nbound
contains
  function createnhelix( nd, center, gap, na, pch) result (nsaa) {
    type( nfilter)                     :: nsaa   # needed by nhelicon
    integer, dimension(:), intent(in)  :: nd, na # data and filter axes
    integer, dimension(:), intent(in)  :: center # normally (na1/2,na2/2,...,1)
    integer, dimension(:), intent(in)  :: gap    # normally ( 0,   0,  0,...,0)
    integer, dimension(:), intent(in)  :: pch	 # (prod(nd)) patching
    type( filter)                      :: aa
    integer                            :: n123, np, ip
    integer, dimension(:), allocatable :: nh
    aa = createhelix( nd, center, gap, na)
    n123 = product( nd);  np = maxval(pch)
    allocate (nh (np)); nh = size (aa%lag)
    call nallocate( nsaa, nh, pch)
    do ip = 1, np
       nsaa%hlx( ip)%lag = aa%lag
    call deallocatehelix (aa)
    call nboundn( nd, na, nsaa) 
    }
}