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Re: REGRESS Question [message #36722 is a reply to message #31982]

Wed, 22 October 2003 03:44

Chris Lee
Messages: 101
Registered: August 2003

Senior Member

In article <932b9720.0310210627.f93c6f2@posting.google.com>, "Kevin M.
Lausten" <kevinlausten@hotmail.com> wrote:

> I am having difficulty working with the REGRESS function. I continually
> get values <1 for my slope when doing a regression between two vectors.
> When I do a regression mapping y to x (slope = regress(x, y, const =
> const)) and when I do a regression mapping x to y (slope = regress(y, x,
> const = const) I get a slope<1 for both calculations. Shouldn't the
> y=mx+b of these two regressions be inverses of each other (leading to
> one slope>1, and one<1?) Maybe I am misunderstanding regressions?
> Thanks,
> kevin

Hi,

If you try the regression with the simplest possible straight line

y = mx +c

where m=1 and c=0 , so

y=x

if you regress with y=f(x), you get a value of 1 (and a constant of 0)
if you regress with x=f(y), you get a value of 1, again.

if the gradient is negative for y=f(x), it has to be negative for x=f(y).
The two equations you are assuming in the regressions are

y= mx + c OR x = (y-c)/m = ny + d

n=1/m, so sign is preserved. (and d=-c/m = -cn)

HTH

Chris.

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[Message index]

		REGRESS Question By: David Fanning on Wed, 04 September 2002 14:21
		Re: REGRESS Question By: Mike Alport on Fri, 06 September 2002 00:26
		Re: REGRESS Question By: julia[1] on Thu, 05 September 2002 11:31
		Re: REGRESS Question By: William Clodius on Thu, 05 September 2002 10:31
		Re: REGRESS Question By: justspam03 on Wed, 22 October 2003 07:01
		Re: REGRESS Question By: wmconnolley on Wed, 22 October 2003 06:03
		Re: REGRESS Question By: Chris Lee on Wed, 22 October 2003 03:44
		Re: regress question By: Wout De Nolf on Mon, 01 December 2008 00:38
		Re: regress question By: mccreigh on Sun, 30 November 2008 23:42
		Re: regress question By: Kenneth P. Bowman on Sat, 29 November 2008 07:58
		Re: regress question By: Brian Larsen on Thu, 27 November 2008 07:37
		Re: regress question By: Wout De Nolf on Thu, 27 November 2008 02:47

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