I'd like to carry out a discrete fourier transformer on some data but
attempts so far have not been successful.
I've been able to do an FFT in the following manner:
def mmag(a):
return sqrt(a[0]^2+a[1]^2)
a = FastFourierTransform(4)
a[0]=0.707
a[1]=-0.707
a[2]=-0.707
a[3]=0.707
print a
print a.forward_transform()
print [mmag(kk) for kk in a]
However I don't know how to do the magnitude properly (I tried abs, norm
and was not able to get either to work).
However to sort out the DFT:
J = range(4)
B = [707/1000,-707/1000,-707/1000,707/1000]
A = [QQ(i) for i in B]
print A
s = IndexedSequence(A,J)
print s.dft()
This gives me:
[(0.707, 0.0), (-0.707, 0.0), (-0.707, 0.0), (0.707, 0.0)]
None
[0.0, 1.999697977195556, 0.0, 1.9996979771955563]
[707/1000, -707/1000, -707/1000, 707/1000]
Indexed sequence: [0, -707/500*zeta4 + 707/500, 0, 707/500*zeta4 + 707/500]
indexed by [0, 1, 2, 3]
Is this the expected result? I was not expecting the zeta4 multiplies and was
hoping to get the same result as the FFT above.
regards
Dan
--
--
Private or confidential message? Public Key available here
<https://pgp.mit.edu/pks/lookup?search=dan.mulholland%40gmail.com&op=index>
:
--
You received this message because you are subscribed to the Google Groups
"sage-support" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/sage-support.
For more options, visit https://groups.google.com/d/optout.
