Date:         Wed, 30 Nov 2011 19:33:08 +0800
Reply-To:     Murphy Choy <goladin@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Murphy Choy <goladin@GMAIL.COM>
Subject:      Re: Unable to fit the model with PROC NLIN
Comments: To: SUBSCRIBE SAS-L Anonymous <rkbattula@drreddys.com>
In-Reply-To:  <201111300945.pAU2kqaZ025468@waikiki.cc.uga.edu>
Content-Type: text/plain; charset=ISO-8859-1

I think there are too few observations for any modeling purposes.

On Wed, Nov 30, 2011 at 5:45 PM, SUBSCRIBE SAS-L Anonymous <
rkbattula@drreddys.com> wrote:

> Hi every body,
>
> I tried to fit the model with three observations. I have three different
> doses and their PD responses. I used following code:
>
> proc nlin data = it method=marquardt hougaard;
>  parms E0 =1  ED50 =1  Emax = 1 ;  parameters;
>  model FFEP=E0 + ((Emax * Dose) / (ED50 + Dose));
>  Der.E0   = 1;
>  Der.Emax = Dose / ( ED50 + Dose);
>  Der.ED50 = - (( Emax * Dose)/ ((ED50 + Dose)**2));
>  output out=pred p=yhat;
> run;
>
> Model is not able to fit since I have only three observations. Is there
> any way to work on this? Your help is greatly appriciated.
>
> Thanks,
>
> krishna.
>



--
Regards,
Murphy Choy

Certified Advanced Programmer for SAS V9
Certified Basic Programmer for SAS V9
DataShaping Certified SAS Professional