Rationale for 15C L.R. result order? « Next Oldest | Next Newest »

 ▼ Mike Fikes Junior Member Posts: 7 Threads: 2 Joined: Jul 2011 09-20-2011, 03:31 PM I suspect that, in most scenarios, the slope of a given line is more "meaningful" than the value of its y-intercept, yet the L.R. operation on the 15C returns the slope in the Y register. (A criticism of this choice is made in "HP-15C: FIRST IMPRESSIONS OF AN HP-41 USER" attached by Gene Wright to Some 15c files from HHC 2010 recently.) Is there a logical argument that can be used to defend the choice that HP made for the 15C? Perhaps it facilitates certain use cases? Edited: 20 Sept 2011, 4:09 p.m. after one or more responses were posted ▼ Walter B Posting Freak Posts: 4,587 Threads: 105 Joined: Jul 2005 09-20-2011, 04:00 PM Can't tell you a logical argument but only an historical. L.R. returns the regression parameters in this order since the HP-32E at least. So we did keep it this way for the WP 34S, too. Addendum: Quote: A criticism of this choice is made in "HP-15C: FIRST IMPRESSIONS OF AN HP-41 USER" Hmmh, the author of that article only claims the reverse order would be "more natural" without giving any rationale for this claim :-/ Looks like there are simply just two ways and HP chose one :-) Edited: 20 Sept 2011, 4:09 p.m. ▼ Mike Fikes Junior Member Posts: 7 Threads: 2 Joined: Jul 2011 09-20-2011, 04:14 PM Right. With respect to being more "natural" I would argue that (to me at least) it would have been more natural, in the following sense: In algebra class, you learn the formula for a line is y = mx + b. Because of this, I expect m to be "first" (in the X register), followed by b in the Y register. ▼ Walter B Posting Freak Posts: 4,587 Threads: 105 Joined: Jul 2005 09-20-2011, 05:05 PM Well, what's pushed on the stack first ends higher up :-) So what you see may be the consequence of m ENTER b . BTW, what's the rationale behind the abbreviations "m" and "b"? ▼ Mike Fikes Junior Member Posts: 7 Threads: 2 Joined: Jul 2011 09-20-2011, 05:19 PM Good question :) Evidently even John Conway put forth a conjecture on this one. (Presumably the John Conway.) Edited: 20 Sept 2011, 5:28 p.m. Martin Pinckney Posting Freak Posts: 1,248 Threads: 33 Joined: Aug 2007 09-20-2011, 10:08 PM Quote: BTW, what's the rationale behind the abbreviations "m" and "b"? It has always been thus... ▼ Gerson W. Barbosa Posting Freak Posts: 2,761 Threads: 100 Joined: Jul 2005 ▼ Walter B Posting Freak Posts: 4,587 Threads: 105 Joined: Jul 2005 09-21-2011, 02:12 AM Olá Gerson, obrigado! Interesting article :-) Dieter Senior Member Posts: 653 Threads: 26 Joined: Aug 2010 09-21-2011, 01:21 PM Well, of course real statisticians (tm) know that simple linear regression is just a warm-up for the real thing (multiple linear and nonlinear regression). They usually think further and use models with a larger number of variables. And so we finally get ``` y = a0 + a1x1 + a2x2 + a3x3 + ... ``` So it's fine that a0 is returned in X and a1 in Y. :-) Dieter Crawl Senior Member Posts: 306 Threads: 3 Joined: Sep 2009 09-20-2011, 05:59 PM My guess: For estimating x. There already is an estimating y function, but not for x. To estimate x, you'd do 1. LR 2. CHS 3. y 4. + 5. Swap 6. divide If the m, b order was different, it seems you'd want to do the same steps, but add an extra swap to get it to what it currently is. So why not have the swap built in?

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