From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20617 invoked by alias); 17 Jun 2009 22:52:03 -0000 Received: (qmail 20606 invoked by uid 22791); 17 Jun 2009 22:52:02 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,SARE_MSGID_LONG40,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mail-ew0-f228.google.com (HELO mail-ew0-f228.google.com) (209.85.219.228) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 17 Jun 2009 22:51:56 +0000 Received: by ewy28 with SMTP id 28so963455ewy.24 for ; Wed, 17 Jun 2009 15:51:53 -0700 (PDT) MIME-Version: 1.0 Received: by 10.210.88.3 with SMTP id l3mr3483881ebb.59.1245279113249; Wed, 17 Jun 2009 15:51:53 -0700 (PDT) In-Reply-To: <20090617221222.GA31761@hippogriff.homeunix.org> References: <20090614165708.22998.15238.stgit@localhost> <4a00655d0906150743h73d5d019w58a32db374861309@mail.gmail.com> <20090615173917.GA31020@hippogriff.homeunix.org> <4a00655d0906151113y5efb05a7gde0b73d7afc9d0bf@mail.gmail.com> <20090615183150.GA6198@hippogriff.homeunix.org> <4a00655d0906171454h411b717ao842bdb618513e3b9@mail.gmail.com> <20090617221222.GA31761@hippogriff.homeunix.org> From: Rhys Ulerich Date: Wed, 17 Jun 2009 22:52:00 -0000 Message-ID: <4a00655d0906171551j3557799g75fe5bc8e59b0986@mail.gmail.com> Subject: Re: [PATCH] Add Greville abscissae functionality to B-splines To: Patrick Alken Cc: gsl-discuss@sourceware.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Mailing-List: contact gsl-discuss-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gsl-discuss-owner@sourceware.org X-SW-Source: 2009-q2/txt/msg00026.txt.bz2 Hi Patrick, I'm fine if you'd like to back out the previous patch until you can review the two applied together. The trap I fell into is that, confusingly, the indexing of the abscissa as it usually appears excludes the very first and very last knots in GSL's w->knots vector. Apparently this is a common convention I didn't know about until I ran into a friend in the hall today. Also, the abscissa location should be averaged over degree (w->km1) knots and not order (w->k) knots. > I also found a matlab code on it which I used to verify some of your > test cases, which did look correct. Odds are good that you can get the new unit tests will also look okay against that same Matlab code if you (a) throw out the first and last knot, and (b) use the degree and not the order. The new patch's documentation includes a reference to a 2005 paper by Johnson that gives both a definition and an example set of knots/abscissae for a C3 quartic (Figure 2) if you'd like another comparison point. Have a good trip, Rhys