mean_array Subroutine

  subroutine mean_array(nside, cube, cube_mean)
    !! Average cube along spatial axis depending on level n 
    implicit none

    integer, intent(in) :: nside !! nside of the cube
    real(xp), intent(in), dimension(:,:,:), allocatable :: cube !! cube
    real(xp), intent(inout), dimension(:,:,:), allocatable :: cube_mean !! average cube

    integer :: i, j, k, l, n
    real(xp), dimension(:), allocatable :: spectrum

    allocate(spectrum(size(cube,dim=1)))
    spectrum = 0.
    
    n = size(cube, dim=2) / nside

    do i=1,size(cube_mean,dim=2)
       do j=1,size(cube_mean,dim=3)
          do k=1,n
             do l=1,n
                spectrum = spectrum + cube(:,k+((i-1)*n),l+((j-1)*n))
             enddo
          enddo
          spectrum = spectrum / (n**2)
          cube_mean(:,i,j) = spectrum
          spectrum = 0.
       enddo
    enddo
    
  end subroutine mean_array