----- Original Message -----
From: Wen-Feng Hsiao <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, April 13, 2000 3:06 AM
Subject: linear model or interactive model?
| Dear all,
|
| Suppose I have an aggregation model which is in the following form:
| Y = c1*(X11 * X12) + c2*(X21 * X22)?
|
| This model could be thought as an aggregation of two knowledge, namely
| X1. and X2.. Each knowledge contains two pieces of information
| (attributes). For example, X1 contains X11 ans X12. Now if X.1 is the
| height, and X.2 is the weight of a person. Then, the aggregation of any
| two persons, say, Student1(height=170cm, weight=60kg),
| Student2(height=180cm, weight=68kg) can be represented by
|
| Y = 170*60+180*68=22440.
|
| My question: a model as the above form is linear or interactive? I doubt
| it is not a linear model. Since it is not in this form: Y= c1 X1 + c2 X2,
| where c1 and c2 are constant. I doubt it is not a pure interactive form,
| since X.1 and X.2 are dependent. Sorry for this stupid question.
|
| Wen-Feng
|
==== Joe Ward writes|
===========================================================================
Wen-Feng---
Your model --
Y = X11 * X12 + X21 * X22.
does not have any unknowns.
Did you mean to write:
Y = c1*(X11 * X12) + c2*(X21 * X22)?
All models of the form:
Y = c1*X1 + c2*X2 + ... + cp*Xp + E
are LINEAR MODELS.
It does not matter what NUMBERS are included in the Xs.
Y = c1*X1 + c2*X2 + c3*(X1*X2) + c4*(X1^2) + c5*(lnX1) + E
is LINEAR in the unknown coefficients c1, c2, ...
The most useful Xs are the BINARY( 1 or 0) predictors.
--- Joe
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