Hi all ---
The power of learning to impose restrictions on
Regression/Linear Models is that you can create models that have the
properties
that YOU
WANT. If YOU WANT TO
CREATE A MODEL WITH "INTERESTING" PROPERTIES FOR YOU, THEN
DO IT.
It is quite simple to impose restrictions that force the
least-squares function to pass through any points that you like.
Also, impose restrictions to force a polynomial to have any
slope at any point you would like, etc.
Any linear restrictions on the parameters are OK.
High School
students can ENJOY using their algebra skills to impose
their restirictions OF INTEREST or they can use SAS and allow the program to
impose the restrictions. Restrictions ("RESTRICT" in SAS) can be
imposed to create ASSUMED MODELS that have desired properties and then further
restrictions ("TEST" in SAS) can be imposed to TEST HYPOTHESES if
desired.
Some simple examples of how this is done can be seen in
INTRODUCTION TO LINEAR MODELS by Ward and Jennings.
--- Joe
**********************************
Joe H. Ward, Jr.
167 East Arrowhead Dr.
San Antonio, TX 78228-2402
Phone: 210-433-6575
Fax: 210-433-2828
Email: [EMAIL PROTECTED]
http://www.northside.isd.tenet.edu/healthww/biostatistics/wardindex
==============================
Health Careers High School
4646 Hamilton Wolfe Road
San Antonio, TX 78229
**********************************
Joe H. Ward, Jr.
167 East Arrowhead Dr.
San Antonio, TX 78228-2402
Phone: 210-433-6575
Fax: 210-433-2828
Email: [EMAIL PROTECTED]
http://www.northside.isd.tenet.edu/healthww/biostatistics/wardindex
==============================
Health Careers High School
4646 Hamilton Wolfe Road
San Antonio, TX 78229
**********************************
----- Original Message -----
From: "Robert J. MacG. Dawson" <[EMAIL PROTECTED]>
To: "Anders" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Thursday, November 20, 2003 8:00 AM
Subject: Re: Best straight line with one fixed
point
>
> Anders wrote:
> >
> > I am using the least-mean-square method to calculate the best straight
> > line to a number of meassured points. But how do I change the formulas
> > if I want one of my meassured points to be fixed (the line must go
> > throu that point). This is possible in Excel, but only to fix the
> > y-value at x=0. I presume it is mathematically possible but havn't
> > found any formula for it.
>
> There are, as usual, infinitely many ways that you *can* do it. I can
> think of about three plausible ones off the top of my head.
>
> The question you need to answer first is - why do you want to do it?
> This affects what the correct way to do it would be (and whether it
> would be a smart thing to do at all!)
>
> -Robert Dawson
> .
> .
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