---------- Forwarded message ----------
From: Ahmed Attia <ahmedatia80 at gmail.com>
Date: Mon, Jan 14, 2013 at 2:31 AM
Subject: Help with nonlinear regression
To: r-help at r-project.org
Dears-
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.attia at ag.tamu.edu
Cell phone: 001-979-248-5215