Cassandra Jean and Talk:Linear least squares/Archive 4: Difference between pages

Revision as of 23:09, 29 October 2005

Revision as of 23:09, 29 October 2005

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==Relevancy==

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03:33, 26 October 2005 Oleg Alexandrov m (I don't find the octave code particularly relevant;)

Contestant on America's Next Top Model-Cycle 5. Walked out (quit) refusing to cut her hair.

It's very relevant. Actually calculating this is interesting, not just knowing how to calculate it with pen and paper. --[[User:marvinXP|marvinXP]] ([[User talk:marvinXP|talk]])

: You are reffering to [http://en.wikipedia.org/w/index.php?title=Linear_least_squares&diff=26499866&oldid=26450807 this].

: I am myself doing numerical analysis for living, use Matlab (of whom Octave is a clone) and have no bias against numerical programs. However, that piece of code is just rewiting the formula

::<math> A^T \! A \mathbf{x} = A^T \mathbf{b}, </math>

:from the article in Octave's notation. It is a trivial exercise I would say, and not worth its place in the article. [[User:Oleg Alexandrov|Oleg Alexandrov]] ([[User talk:Oleg Alexandrov|talk]]) 06:04, 26 October 2005 (UTC)

::I agree. Actually, I would have deleted the Octave fragment if I had time to do so before Oleg did. -- [[User:Jitse Niesen|Jitse Niesen]] ([[User talk:Jitse Niesen|talk]]) 11:10, 26 October 2005 (UTC)

:::I see your point, but I disaree. A non-mathematician may want to actually use the formula. It's a very practical application. It's not a matter of "this is how it's written in program X", but rather "if you have the values, you can plug it into this free program, and have the result presented to you". I'd say most people who'd want to calculate this (let's assume they know <b>of</b> least squares), may not know octave, or matlab or any other math-program besides a simple calculator. And may not afford mathlab. --[[User:marvinXP|marvinXP]] ([[User talk:marvinXP|talk]]), 16:24, 29 October 2005 (UTC)

::Even if it is true that most people who know about least squares and want to calculate a least-squares solution, do not know that there are programs for doing so (which I doubt), it would be irrelevant for this article, because it's not a statement specifically about least squares. Many mathematical concepts can be calculated by programs, free or otherwise. I think it would be silly to add this fact to articles like [[matrix multiplication]] and [[matrix inversion]]. By the way, your Octave fragment is suboptimal. As a general rule, one should try to avoid inverting a matrix. The proper way is to use the slash, as follows:

:::<tt>A = [0,1; 2,1; 4,1; -1,1]</tt>

:::<tt>b = [3; 3; 4; 2]</tt>

:::<tt>x = A \ b</tt>

::-- [[User:Jitse Niesen|Jitse Niesen]] ([[User talk:Jitse Niesen|talk]]) 17:51, 29 October 2005 (UTC)

::I'd consider matrix multiplication less directly applicable, and would just involve defining '*' in a given program. This example had more steps to it (well it had before you showed the backslash operator, thank btw). But I guess I'll concede. --[[User:marvinXP|marvinXP]] ([[User talk:marvinXP|talk]]), 23:09, 29 October 2005 (UTC)