Question

I have seen this video on the Fast Fourier Transform but I don't know how the matrix is applied in practical use.

So for instance:

Answer 1

\[\LARGE F_4=\left[\begin{matrix}1 & 1 & 1 & 1\\ 1 & i & -1 & -i\\ 1 & -1 & 1 & -1\\ 1 & -i & -1 & i\end{matrix}\right]\]

What do I do with this matrix to Fourier Transform anything?

Answer 2

i dont know much but it is a 4 point Discrete Forier Transform

Answer 3

So what does that mean exactly, suppose I want to take the fourier transform of a triangle function with this, what would I do?

Answer 4

we get this matrix after taking fourier transform ..that is discrete F.T......

Answer 5

So how do we get this? I only understand the regular old fourier series and fourier transform I'm afraid. I don't really know where this matrix comes from at all obviously but I understand the concepts of that stuff.

Answer 6

it would be better if ask any professer....he could make u understand well

Answer 7

I'm not taking any math classes this semester. I just want to know where this falls in because it sort of just randomly came up in this series of lectures.

I am under the impression we are sampling some wave form at discrete points in time and using this to get the frequencies but I'm not sure how at all this matrix is part of this picture.

Answer 8

its complicated ...i suggest u to check discrete fourier transform..sorry to say ..but i have not much idea...thatzz why i m unable to help

Answer 9

hmm...like http://en.wikipedia.org/wiki/DFT_matrix

Answer 10

check this ...wiki.....may be little bit helpful to u

Answer 11

I do understand why this is considered the fast fourier transform in that it is able to bring the computation down from n^2 time to (n*logn)/2 time since it is just a clever trick with linear algebra.

Thanks I'll check it out.

Answer 12

also check this link this will much helpful to you
http://www.katjaas.nl/fourier/fourier.html

Answer 13

Oh that wikipedia page actually explains exactly what I was looking for quite well thanks. Usually wikipedia articles are dense and not very good at explaining things to me.

Answer 14

yeah but i studied it when i had this topic ..so i gave you ..n it helped me....but it was like i got it but if someone ask me to explain it i can't lol

Answer 15

Yeah these are really good thanks. =D

Answer 16

welcome :)