Date: Thu, 19 Feb 2009 08:44:02 -0500
Reply-To: Ligia Buia <ligia.buia@GMAIL.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: Ligia Buia <ligia.buia@GMAIL.COM>
Subject: Re: nonlinear best-fit line
In-Reply-To: <941871A13165C2418EC144ACB212BDB0BEB2EF@dshsmxoly1504g.dshs.wa.lcl>
Content-Type: text/plain; charset=ISO-8859-1
I am looking at the values of a biological marker since time of disease
diagnosis. Each point on my scatterplot represents a different person, but
the time since disease diagnosis at which the lab was drawn varies (with
most points occurring within 4 months of diagnosis). I think there might be
a "dip" in values at some point and a linear, straight best fit line is
obviously obscuring that. I would like to plot a best fit line that
minimizes my residuals at each point in time. And also, look at a trend
test statistic. Hope that makes it more clear... Thank you for your time.
On Wed, Feb 18, 2009 at 6:30 PM, Nordlund, Dan (DSHS/RDA) <
NordlDJ@dshs.wa.gov> wrote:
> > -----Original Message-----
> > From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On
> > Behalf Of Ligia Buia
> > Sent: Wednesday, February 18, 2009 2:38 PM
> > To: SAS-L@LISTSERV.UGA.EDU
> > Subject: nonlinear best-fit line
> >
> > Good afternoon,
> >
> > I am having trouble trying to figure out how to fit a
> > nonlinear best fit
> > line to my data in SAS. Any help would be greatly appreciated.
> >
> > Regards,
> >
> > Ligia
> >
> >
> I think you will need to provide more information to get any useful advice.
> There are ways to do nonlinear estimation in a variety of contexts. You
> can also compute a fit for curvilinear data using linear regression
> techniques. So can you tell us what your data look like, and what the
> context is for this project?
>
> Dan
>
> Daniel J. Nordlund
> Washington State Department of Social and Health Services
> Planning, Performance, and Accountability
> Research and Data Analysis Division
> Olympia, WA 98504-5204
>
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