Jenny Sun
2008-May-27 06:10 UTC
[R] How to test significant differences for non-linearrelationships for two locations
Thanks for the reply! I thought of dummy variable. But I have no idea how to put the dummy into the model. Say I have a Y~ X relationship in logistic form as: nls(Y~a/(1+b*exp(-c*X),start=c(a=1,b=1,c=1) assume I am using nls to solve the question. where could I put the dummy variable? Thanks! Jenny> is it possible for you to include the site as a dummy 0-1 and then >use just one logistic model rather than two ? this way, the test of >whether site >matters would be easier to do using say a likelihood ratio test of the >full model versus sub model. then, if the site dummy is significant, >that >means the relationships for the two sites are significantly different. > > > > >On Tue, May 27, 2008 at 2:23 AM, Jenny Sun wrote: > >> Hi List, >> >> I have to compare a relationship between y and x for two locations. I >> found logistic regression fits both datasets well, but I am not sure >> how to test if relationships for both sites are significantly >> different. I searched the r site, however no answers exactly match the >> question. >> >> I used Tukey's HSD to compare two means, but the relationship in my >> study was not simply linear. So I was wondering if there is anyone had >> experience in making such comparisons. Thanks in advance! >> >> Jenny >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help at r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code.
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