program DFT
implicit none
integer :: k, N, x, y, j, r, l, istat, p
integer, parameter :: dp = selected_real_kind(15,300)
real, allocatable,dimension(:) :: h
complex, allocatable, dimension(:) :: rst
complex, dimension(:,:), allocatable :: W
real(kind=dp) :: pi
p = 2*pi
!open file to write results to
open(unit=100, file="dft.dat", status='replace')

N = 400
!allocate arrays as length N, apart from W (NxN)
allocate(h(N))
allocate(rst(N))
allocate(W(-N/2:N/2,1:N))

pi = 3.14159265359
!loop to create the sample containing array
do k=1,N
  h(k) = k*(pi*0.005)
end do

!loop to fill the product matrix with values
do j = -N/2,N/2
do k = 1, N

	W(j,k) = EXP((2.0_dp*pi*cmplx(0.0_dp,1.0_dp)*j*k)/N)

end do
end do
!use of matmul command to multiply matrices
rst = matmul(W,h)
print *, h, w
write(100,*) rst

end program