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Re: NLME: Design Matrices

To: Savitri Appana <saviappana@yahoo.com>
Subject: Re: NLME: Design Matrices
From: Spencer Graves <spencer.graves@pdf.com>
Date: Wed, 14 Jun 2006 19:55:52 -0700
Cc: s-news@wubios.wustl.edu
In-reply-to: <20060613200547.75636.qmail@web51907.mail.yahoo.com>
References: <20060613200547.75636.qmail@web51907.mail.yahoo.com>
User-agent: Thunderbird 1.5.0.4 (Windows/20060516)
I don't know, but I'll tell you what I just tried and what I might do if that were my question. First, since you did not provide a self-contained example, I tried the "example" in the "nlme" help page:

fm1 <- nlme(weight ~ SSlogis(Time, Asym, xmid, scal), data = Soybean,
            fixed = Asym + xmid + scal ~ 1, start = c(18, 52, 7.5))

Then I requested "names(fm1)". This led me to examine "fm1$modelStruct", "fm1$dims", etc., one by one. In the past, this has led me to answers to crudely similar questions. In this case, it did not.

Then I typed 'nlme' at a command prompt to look at the code. This function primarily consists of a call to "UseMethod". So I tried "methods('nlme')". This identified "nlme.formula" and "nlme.nlsList". I'd list one or the other, depending on which one you actually used, and then copy that code into a script file and walk through it line by line. If you do that, I'm confident you will find enlightment, at least on this question.

          hope this helps.
          spencer graves

Savitri Appana wrote:
Hello Everyone,

How can I get S-plus to reproduce the design matrices
A and B for the fixed and random effects,
respectively, for a given nlme model.


Thank you,
Savi


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