On Apr 27, 2011, at 9:28 AM, Schatzi wrote:
Here is more information on the equation. It is a growth function:
Growth = a + b*(1-exp(-k*time))
where a, b and k are parameters. I wanted to test the difference in
total growth between treatments and the parameters a + b represent
total growth. Thus, I figured that I could add the parameters and
the SE to test the treatment differences. I also need the rate
constant k and the initial values a and their treatment differences.
I found the equation I posted on this website:
http://sci.tech-archive.net/Archive/sci.math/2004-07/4780.html
This book was referenced: Kendall & Stuart's Advanced Theory of
Statistics
You should look at the vignettes and examples in the `fda` package.
fda == Functional Data Analysis and the authors have a book that adds
further background.
http://ego.psych.mcgill.ca/misc/fda/ex-growth-a2.html
You might also try:
RSiteSearch("growth curve")
--
David.
Thanks for all you your help.
Adele
From: ml-node+3477116-1659458804-211...@n4.nabble.com [mailto:ml-node+3477116-1659458804-211...@n4.nabble.com
]
Sent: Tuesday, April 26, 2011 09:29 PM
To: Thompson, Adele - adele_thomp...@cargill.com
Subject: Re: How can I extract information from list which class is
nls
On Tue, Apr 26, 2011 at 2:21 PM, Schatzi <[hidden email]</user/
SendEmail.jtp?type=node&node=3477116&i=0&by-user=t>> wrote:
How do I extract the standard error of the parameter estimates?
Also, if I would like to add two parameters together (x+y), can I
use this
equation to calculate the new standard error?:
x = parameter 1
y = parameter 2
xSE = SE parameter 1
ySE = SE parameter 2
NewSE=(x+y)*sqrt((xSE/x)^2+(ySE/y)^2)
Try taking the square roots of their variance:
example(nls)
sqrt(diag(vcov(fm1DNase1)))
Asym xmid scal
0.07815395 0.08135321 0.03227080
# it gives the same result as another solution
# offered on this thread
coef(summary(fm1DNase1))[, "Std. Error"]
Asym xmid scal
0.07815395 0.08135321 0.03227080
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Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com
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