[R] Non-negative solutions to complicated equations

[Ravi Varadhan]

Hi,

I found at least 2 typos in your function.  Can you check your equations
carefully to make sure that they are correct and then send me a reproducible
version of the code that I can cut and paste into my R session?

Ravi. 


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Ravi Varadhan, Ph.D.

Assistant Professor, The Center on Aging and Health

Division of Geriatric Medicine and Gerontology 

Johns Hopkins University

Ph: (410) 502-2619

Fax: (410) 614-9625

Email: rvaradhan at jhmi.edu

Webpage:
http://www.jhsph.edu/agingandhealth/People/Faculty_personal_pages/Varadhan.h
tml

 

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-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of stenort
Sent: Thursday, July 23, 2009 6:08 AM
To: r-help at r-project.org
Subject: [R] Non-negative solutions to complicated equations


Hi all,
I have a system of 3 equations with many defined parameters and 3 variables
I need to find solutions to. I actually know the solutions I'm aiming for
(0.07,0.287,0.0061) but R tends to give me (0,0,0).
I tried the "BB" package but don't really follow how to refine my solutions
from that; these are wrong so far. Here's my code from trying that:
> f<-function(x){
+ x1<-x[1]
+ x2<-x[2]
+ x3<-x[3]
+ 
+ F<-rep(NA,3)
+ F[1]<-(0.075*x3+0,175*x2)*0.065*exp(-0.03*25)
+ F[2]<-(x2/0.075)*((1/50)/(0.065*0.5.125*0.872214*(1-(x2*(56/25))))-0.1
+ 75)
+ F[3]<-(x3/0.175)*((1/70)/(0.065*0.366*0.872214*(1-(x3*(66/35))))-0.075
+ )
+ return(F)
+ }
> p0<-c(0.1,0.1,0.1)
> dfsane(par=p0,fn=f,control=list(maxit=3000))


I have substituted estimated values for all the parameters into the above
equations.
Thanks
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