Hi, I spent a fair amount of time today debugging what I thought was a bug in the scaling of psd() when I was using NFFT to specify zero-padding. This was a mis-use of the code on my part, where I should have been using pad_to to get zero-padding. Most embarassing about this is that I'm basically the maintainer of record for this code and responsible for the most recent changes, part of which improved 0-padding. (> 2 years ago)
I've come to the conclusion that if I was able to get it wrong, it's likely that this issue has bitten and will bite other users. The problem stems from the fact that the code underlying psd (and csd, etc.) will gladly pad your data to NFFT if len(x) < NFFT. The extra 0's added here throw off the scaling (whereas using pad_to does not). [Aside for the curious: The NFFT-padding code pre-dates the use of pad_to for zero-padding and was left so-as not to break code, not realizing that leaving it was still wrong.] Options: 1) Rip out the code that does the zero-padding based on NFFT and raise an exception in the case that len(x) < NFFT. 2) Issue a warning on len(x) < NFFT for awhile, and then rip it out. 3) ? I'm really tempted to just go with 1), with an exception that details the problem and the fix. While this would break existing code, this code is almost 100% guaranteed to be broken and silently producing the incorrect answer (unless code was already hacking around our broken-ness, which wouldn't be easy.) I still need to go through and convince myself that there's not some use-case where NFFT > len(x) would produce correct and desired behavior, which isn't covered by pad_to. What I'm looking for is thoughts from devs on breaking backwards compatibility and from users, whose code may or may not be broken by such a change. Ryan -- Ryan May Graduate Research Assistant School of Meteorology University of Oklahoma ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today http://p.sf.net/sfu/msIE9-sfdev2dev _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
