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<DIV><FONT size=2>Hi all,</FONT></DIV>
<DIV><FONT size=2>1. Can nonlinear models be used in gee? For example, I have a
dataset which contains 2 variables x and y, I wrote</FONT></DIV>
<DIV><FONT size=2>data(ex)</FONT></DIV>
<DIV><FONT size=2>atttach(ex)</FONT></DIV>
<DIV><FONT size=2>a<-100</FONT></DIV>
<DIV><FONT size=2>b<- -0.5</FONT></DIV>
<DIV><FONT size=2>c<-4.5</FONT></DIV>
<DIV><FONT size=2>d<-20</FONT></DIV>
<DIV><FONT size=2>Then:</FONT></DIV>
<DIV><FONT size=2>a. y~gee(y~d+(a-d)/(1+(x/c)^b))</FONT></DIV>
<DIV><FONT size=2>Error in terms.formula(formula, data = data) :
<BR> invalid power in
formula</FONT></DIV>
<DIV><FONT size=2>b. y~gee(y~d+(a-d)/(1+(x/c))</FONT></DIV>
<DIV><FONT size=2>Error in model.frame(formula, rownames, variables, varnames,
extras, extranames, : <BR>
variable lengths differ</FONT></DIV>
<DIV><FONT size=2>Why?</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Thanks!</FONT></DIV>
<DIV><FONT size=2>Sincerely Yours,<BR>Jinn-Yuh Guh, M.D.<BR>Dept. of Internal
Medicine<BR>Kaohsiung Medical College<BR>100 Shi-Chuan 1st Road<BR>Kaohsiung,
Taiwan<BR>FAX: 886-7-312-2810<BR>e-mail: <A
href="mailto:jyuh@mail.nsysu.edu.tw">jyuh@mail.nsysu.edu.tw</A></FONT></DIV>
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