---------- Forwarded message ----------
From: <r-help-owner@r-project.org>
Date: Mon, Jan 14, 2013 at 12:31 AM
Subject: Help with nonlinear regression
To: ahmedatia80@gmail.com


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---------- Forwarded message ----------
From: Ahmed Attia <ahmedatia80@gmail.com>
To: r-help@r-project.org
Cc:
Date: Mon, 14 Jan 2013 00:31:41 -0800
Subject: Help with nonlinear regression



  Hi-

 I have a question about nonlinear regression.
*Asymptotic Regression Model**
* * below is the equation of the model  (Reference the R book page 662)*

y = a - b e^-cx when I compensate x with 50 for instance, I get a very high
value does not match the graph produced by the same model (Asymptotic
regression model).

 below is the output analysis from R;

 Formula: GN1 ~ SSasymp(nrate, a, b, c)

 Parameters:
  Estimate Std. Error t value Pr(>|t|)
a  12.8190     0.4407   29.09 8.92e-05 ***
b   5.7249     0.2803   20.42 0.000257 ***
c  -4.6697     0.1703  -27.41 0.000107 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

 Residual standard error: 0.2874 on 3 degrees of freedom

 Number of iterations to convergence: 0
Achieved convergence tolerance: 7.184e-06

 >

 based on these coefficients  should y= 12.81 – 5.72 e4.66x   ?

the predicted lines indicate that the model works fine, but I do not know
how to compensate x in the equation to get y


AA






-- 
Ahmed M. Attia


Research Assistant
Dept. Of Soil&Crop Sciences
Texas A&M University
ahmed <ahmedatia@zu.edu.eg>.attia@ag.tamu.edu
Cell phone: 001-979-248-5215

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