Daniela--
Does "nonlinear" refer to a LINEAR MODEL of the form:
Y = a1*X1 + a2*X2 + a3*X3 + a4*X4 +... + ap*Xp + E
where
X1 = U - a predictor of all 1s.
X2 = X - any numerical predictor
X3 = X^2 - the "squares" of the elements in X
X4 = X^3 - the "cubes" of the elements in X
etc.?
If this is the situation you can do wonderful things with
a general polynomial form. You can use an nth degree
polynomial and impose retrictions that allow you much
flexibility about the shape of your curve. For example,
you might choose to start with a 6th degree form and
then impose restrictions FOR THE RANGE OF INTEREST
ON THE X VARIABLE that allow you to use part of the
function that has ONE wiggle (hump), TWO wiggles (humps),
etc. You can FORCE any "undesired" wiggles (humps) to occur
OUTSIDE your RANGE OF INTEREST.
-- Joe
****************************************************************************
****
Joe Ward.........................................Health Careers High School
167 East Arrowhead Dr....................4646 Hamilton Wolfe
San Antonio, TX 78228-2402...........San Antonio, TX 78229
Phone: 210-433-6575.......................Phone: 210-617-5400
Fax: 210-433-2828............................Fax: 210-617-5423
Email: [EMAIL PROTECTED]
http://www.ijoa.org/joeward/watdindex.html
***************************************************************************
----- Original Message -----
From: "Daniela Ichim" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, July 18, 2000 12:17 PM
Subject: bump hunting in nonlinear regression
>
>
> In a nonlinear (univariate) regression problem, specifically
> a calibration problem in thermometrics, I have the problem of
> testing whether a curve expressing a relationship between
> Electrical Resistance and Temperature is monotone
> versus the possibility of it having bumps inverting the monotonicity.
>
> The problem of checking the existance of bumps becomes difficult
> especially
> in the regions of sparse data.
>
> I would like directions to the existing related statistical literature.
> Thanks.
>
>
>
>
>
>
>
> =================================================================
> Instructions for joining and leaving this list and remarks about
> the problem of INAPPROPRIATE MESSAGES are available at
> http://jse.stat.ncsu.edu/
> =================================================================
>
=================================================================
Instructions for joining and leaving this list and remarks about
the problem of INAPPROPRIATE MESSAGES are available at
http://jse.stat.ncsu.edu/
=================================================================
