Date:         Fri, 14 Mar 2008 14:11:16 -0400
Reply-To:     msz03@albany.edu
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Mike Zdeb <msz03@ALBANY.EDU>
Subject:      Re: segmented regression problem
Content-Type: text/plain;charset=iso-8859-1

Hi ... if you are willing to try something other than SAS, you can use the National Cancer
Institute's JOINPOINT software ...

http://srab.cancer.gov/joinpoint/

or SEGREG ...

http://www.waterlog.info/segreg.htm

("Joinpoint Goddess", "SEGREG Goddess", hmmmm.... not as universal as "SAS Goddess")

--
Mike Zdeb
U@Albany School of Public Health
One University Place
Rensselaer, New York 12144-3456
P/518-402-6479 F/630-604-1475

> Help! I am at risk of losing my SAS goddess stature among grad
> students!
>
> I've been asked for SAS help with something out of my area, but which
> seems common enough in the literature that hopefully someone on the
> list can provide some quick code help.
>
> When analyzing ovarian follicle growth, an important factor is the
> time at which the dominant follicle diverges from the others (follicle
> deviation). This has been done by visual observation of plots of the
> size of largest two follicles (F1 and F2) against time (deviation is
> the time when the lines obviously diverge). A better statistical
> approach is desirable. Segmented regression seems to be apropos.
>
> "Calculated follicle deviation using segmented regression for modeling
> diameter differences in cattle"
> D. R. Bergfelt, L. H. Segoc, M. A. Bega, and O. J. Ginther
> Theriogenology, Volume 59, Issue 8, 15 April 2003, Pages 1811-1825
> Is basically what I'm after, but I don't know how to get it out of
> PROC REG.
>
> So with data like:
>
> subject
> time
> F1-F2 (difference in size of F1 and F2)
>
> How do I get to a calculated time of deviation for each subject?
>
> Thanks,
> Ashley
>
>