[R] Some clarificatins of anova() and summary ()

[John Sorkin]

Ben,
You were quite correct to indicate that Tanmoy should not use the listserver to get answers to his class assignments. Never the less, I do have some sympathy for him. The help pages for the R functions summary, anova, drop1, do not discuss the critically important issue addressed by Tanmoy's class assignment. I believe this is a serious limitation. If users do not understand the differences between the output of these three basic functions, they can easily be led astray. I am not sure who has access to the help pages, but I hope they see this Email and consider modifying the help pages so as to address the important issue highlighted by Tanmoy's class assignment.
John

John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
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>>> Ben Bolker <bolker at ufl.edu> 12/14/2008 12:25 PM >>>



Tanmoy Talukdar wrote:
> 
> I think now I have got some understanding of the things.
> 
> y ~ x1+x2 first adds x1 to the model and then adds x2 .
> But y~x2+x1 adds x2 first, so the value we get are different.
> 
> please correct me if i am wrong.
> 
> 

 You are not wrong.  However, you're wearing out your welcome
a bit by posting very frequent messages to the list. I'd strongly
recommend that you find some more help locally, or find a
copy of Peter Dalgaard's "Introductory Statistics with R",
and try to work through some of these problems on your own
a bit more.  If you can demonstrate that you've really gone
away and read and thought about these things, and articulate
what still doesn't make sense to you about the way R is doing
things, and that we are not simply answering homework questions,
you will probably get useful answers ...

  good luck,
    Ben Bolker


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