tag:blogger.com,1999:blog-835341608950140555.post25248395429328190..comments2013-08-13T14:52:46.290+02:00Comments on Numerical Recipes: The Cooley-Tukey FFT AlgorithmJaimehttp://www.blogger.com/profile/02831887559711602902noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-835341608950140555.post-49757010722290407152013-08-13T14:12:00.427+02:002013-08-13T14:12:00.427+02:00This comment has been removed by the author.3 Wheelshttp://www.blogger.com/profile/01987266225086034095noreply@blogger.comtag:blogger.com,1999:blog-835341608950140555.post-14543868131958851042011-04-17T00:37:46.440+02:002011-04-17T00:37:46.440+02:00Couple years late but this page has been great hel...Couple years late but this page has been great help for a university project!<br /><br />This is my implementation of your functions, I find it runs around 25% faster simply by referencing methods outside of loops:<br /><br />http://pastebin.com/BmHuMwEq<br /><br />I'm still trying to figure out a way of using reduce/list-comprehension to get rid of as much of the loop overhead as possible.<br /><br />Oh, and finally, dft(x) is kinda a moot point, as I'm padding everything I feed to fft_CT(x) with 0s to make the list length a power of 2.Vesuvianhttp://www.blogger.com/profile/05706498021508071759noreply@blogger.comtag:blogger.com,1999:blog-835341608950140555.post-68440643868564434192009-11-04T15:41:49.963+01:002009-11-04T15:41:49.963+01:00hi!
i need to calculate a fft of a matrix. actuall...hi!<br />i need to calculate a fft of a matrix. actually i need it as a part of my program.<br /><br />i read really a lot of different books and inernet pages on the subject of fft, but i still don't know how to use it.<br />i understand why you split the dft, and all related to that, but when it comes to the exact calculations... i just don't know what to do with it.<br /><br />could you help me please? <br />this is my email:<br /><br />kviki_kiki@yahoo.com<br /><br />thanksKikahttp://www.blogger.com/profile/17516856671638207929noreply@blogger.comtag:blogger.com,1999:blog-835341608950140555.post-52286007619274769112009-04-18T08:08:00.000+02:002009-04-18T08:08:00.000+02:00I find your explanation a little confusing. At fi...I find your explanation a little confusing. At first it isn't clear why splitting the DFT sum into two pieces saves us any work... eventually you mention the "detail" that the periodicity of the transform means we only have to calculate the two sums for k up to M-1 rather than N-1. But it is precisely this fact which cuts the work in half.<br /><br />Also I'm pretty sure in the first code listing, lines 13 and 14 should be indented one level deeper. That way all elements of X get divided (for the inverse transform) instead of just the final one!Greg Ballhttp://www.blogger.com/profile/06661985258561000968noreply@blogger.comtag:blogger.com,1999:blog-835341608950140555.post-55840607196824802852009-04-17T02:17:00.000+02:002009-04-17T02:17:00.000+02:00Just to point out a typo: it's "Tukey" not "Turkey...Just to point out a typo: it's "Tukey" not "Turkey". The co-inventor of the FFT was called John Tukey:<br /><br />http://en.wikipedia.org/wiki/John_Tukeystochastixhttp://stochastix.wordpress.com/noreply@blogger.comtag:blogger.com,1999:blog-835341608950140555.post-31497563541934748342009-04-17T01:52:00.000+02:002009-04-17T01:52:00.000+02:00I'm afraid I hit the "publish" button a little too...I'm afraid I hit the "publish" button a little too fast, and you saw a big work-in-progress mess...<br /><br />I have started using MathTran (http://www.mathtran.org) to display TeX on the blog, since plain text wasn't an alternative for FFTs. It does have the reader problem, similar to what goes on with the syntax highlighter, which only works in the blog, not in the reader.<br /><br />I'm not too happy with this solution as it is, so I may go back to generating image files for the formulas off-line and uploading them (the ones you saw nicely on your reader), although it turns producing a math intensive post into a nightmare, specially if you have, as I do, a tendency to spot mistakes very late...Jaimehttp://www.blogger.com/profile/02831887559711602902noreply@blogger.comtag:blogger.com,1999:blog-835341608950140555.post-52628312037715391942009-04-16T22:58:00.000+02:002009-04-16T22:58:00.000+02:00Jaime,
Your first equation shows up in Google Re...Jaime, <br /><br />Your first equation shows up in Google Reader as "tex: X_k \pi" but the other four equations show up as nice graphics. The first equation looks fine when I go directly to your web site, just not in my reader. Is something different about your first TeX expression?Johnhttp://www.blogger.com/profile/07480208135315956118noreply@blogger.com