Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.fsmpi.rwth-aachen.de!newsfeed.straub-nv.de!news-1.dfn.de!news.dfn.de!fu-berlin.de!uni-berlin.de!news.dfncis.de!not-for-mail From: =?windows-1252?Q?Hans-Bernhard_Br=F6ker?= Newsgroups: comp.graphics.apps.gnuplot Subject: Re: Fit 3D Line to data Date: Wed, 25 Feb 2015 19:38:41 +0100 Lines: 12 Message-ID: References: <68e9ed33-a7ef-4106-8730-151263df2011@googlegroups.com> <4c6352e3-3fd5-4efc-a56e-7244067aece5@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Trace: news.dfncis.de jHQUOl1o9LjMZ0PJHPaZHAKIBGWlJpKX/zn4ZAQxXLOCRbtqcv/zRDcYB2 Cancel-Lock: sha1:hS/SryYliLZcF+ycRSwjQuvjCPI= User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 In-Reply-To: <4c6352e3-3fd5-4efc-a56e-7244067aece5@googlegroups.com> Xref: csiph.com comp.graphics.apps.gnuplot:2790 Am 25.02.2015 um 15:28 schrieb Gavin Buxton: > Pick your 3 favourite points and you have a plane! Seriously though I suspect its because you have too few data points.... That's the next part of the problem. A straight line in 3D space has 4 real degrees of freedom. But I know of no implicit equation that really has just 4 parameters. So there will be extraneous parameters in the fit, which would have to be cancelled out by constraints, to avoid interdependencies. All that makes for an even more tricky job to set up for 'fit' than it already is.