persistent fft

fft via a radix2 algorithm

Description

fft via a radix2 algorithm that "recurses" by calling matlab's fft. Rather quick on repeated calls for fft's of the same size, due to persistent variables, but still a little bit slower than matlab's builtin fft.

There is no advantage to using this code over the builtin fft.

Handles complex, vector inputs.

• MATLAB release: MATLAB 7.2 (R2006a)

[Duane Hanselman]

If as you say "There is no advantage to using this code over the builtin fft." then why post this code? Is it simply an example of code not worth posting?

[Stephen Becker]

Duane -- good question. I saw a lot of poorly written fft code that also is MUCH slower than matlab's fft; so this is an improvement over those codes. It also demonstrates two ideas: the radix2 FFT algorithm, and why persistent variables are useful.

For example, using persistent variables in this fashion on the discrete cosine transform can yield code much faster than matlab's dct() function. I hope to post such a code once I get it into polished form.