[R] R in rearranging equations
Hi, can anyone tell me if R can be used to rearrange very complicated equations in terms of one of the variables? I have: dx/dt = a*b*m*y*(1-x)-r*x and, having set: dy/dx = 0, need to rearrange in terms of x. The problem I have is that I don't know how to rearrange equations when the variables are not yet defined (I get messages warning me that x etc can't be found). I'm not sure if R can actually do this (though I know programs like Maxima can) but ideally the solution we get should be in R. I am also aware that this isn't difficult to solve by hand, but the remaining equations I have to work through have up to double the number of variables. Any help will be appreciated! Stenort -- View this message in context: http://www.nabble.com/R-in-rearranging-equations-tp24461619p24461619.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
[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
(.0061,0.287,0.070) 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]<-(x3/0.075)*((1/50)/(0.065*5.125*0.872214*(1-(x3*(56/25-0.075)
+ F[3]<-(x2/0.175)*((1/70)/(0.065*0.366*0.872214*(1-(x2*(66/35-0.175)
+ 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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Re: [R] Non-negative solutions to complicated equations
Hi Ravi, apologies for the typos. I believe these have been corrected, please
see the new version of the question on the forum page
Ravi Varadhan wrote:
>
> 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.
>
>
>
> ---
>
> 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: rvarad...@jhmi.edu
>
> Webpage:
> http://www.jhsph.edu/agingandhealth/People/Faculty_personal_pages/Varadhan.h
> tml
>
>
>
>
>
>
>
> -----Original Message-
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
> On
> Behalf Of stenort
> Sent: Thursday, July 23, 2009 6:08 AM
> To: r-help@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
> --
> View this message in context:
> http://www.nabble.com/Non-negative-solutions-to-complicated-equations-tp2462
> 2867p24622867.html
> Sent from the R help mailing list archive at Nabble.com.
>
> __
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
> __
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
--
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[R] Problem runnin rSymPy
Hi all,
I'm having major difficulty using the rSymPy package this week, but I have
used it without problems before now. Here is an example of what's happening:
> library(rSymPy)
Loading required package: rJava
> sympy("var('a b c d')")
Error in .jcheck() : No running detected. Maybe .jinit() would help.
And I have no idea how to fix it. I Have tried re-installing but that
doesn't seem to work either. Any help would be great, thanks!
--
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__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
