fourier_backtransform.f90

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subroutine fourier_backtransform(fm, mfm)

!-----------------------------------------------------------------------
! transforms the array of Fourier coefficients fm(1:mfm) back into
! an array of radii fr(1:mfm)
!-----------------------------------------------------------------------
  
  use itm_types
  use mod_output
  use mod_parameter
  use plot_data

  implicit none

  real(r8), dimension(mfm), intent(in) :: fm
  integer(itm_i4), intent(in) :: mfm

  real(r8), dimension(mfm) :: fr, theta
  integer(itm_i4) :: i, m

  do i = 1, mfm
    theta(i) = 2._r8 * pi * (i - 1) / dble(mfm - 1)
    fr(i) = fm(1) / 2._r8
    do m = 2, mfm / 2
      fr(i) = fr(i) + fm(2 * m - 1) * cos((m - 1) * theta(i)) &
       + fm(2 * m) * sin((m - 1) * theta(i))
    end do
  end do

  if (xmgrace_output) then
    call plot_data_1d('line', theta, fr, mfm, 'xmgr_boundary_back')
  end if

  return

end subroutine fourier_backtransform