Re: Confused by FFTW output

From: James Van Buskirk (not_valid_at_comcast.net)
Date: 03/15/05 

Date: Tue, 15 Mar 2005 11:45:21 -0700

"Tom" <flurboglarf@mailinator.com> wrote in message
news:1110902452.743346.225880@l41g2000cwc.googlegroups.com...

> ! signal
> do i=1,n
> t=(i-1)*dt-ttot/2
> sig(i)=exp(-a*t*t)
> write(10,*) i,t,sig(i)
> end do
> ! forward FT

The symmetry requirement should lead to sig(n) == sig(2), because
you used 1-based arrays (you could have used 0-based arrays where
sig(n-1) == sig(1), had you chosen to do so...) Your output to
unit 10 doesn't agree with this, so I tried

! signal
do i=1,n
   t=(i-1.5)*dt-ttot/2
   sig(i)=exp(-a*t*t)
   write(10,*) i,t,real(sig(i))
end do
! forward FT

This has the correct symmetry. 

-- 
write(*,*) transfer((/17.392111325966148d0,6.5794487871554595D-85, &
6.0134700243160014d-154/),(/'x'/)); end