plot(fn,-1,1)

could be helpful, hth, Ingmar

On 25 Apr 2007, at 09:15, francogrex wrote:

>
> This below is not solvable with uniroot to find "a":
> fn=function(a){
> b=(0.7/a)-a
> (1/(a+b+1))-0.0025
> }
> uniroot(fn,c(-500,500))  gives
> "Error in uniroot(fn, c(-500, 500)) : f() values at end points not of
> opposite sign"
>
> I read R-help posts and someone wrote a function:
> http://finzi.psych.upenn.edu/R/Rhelp02a/archive/92407.html
> but it is not very precise. Is there any '"standard" function in R  
> that can
> solve this? thanks.
> -- 
> View this message in context: http://www.nabble.com/How-to-solve- 
> difficult-equations--tf3643595.html#a10175603
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@stat.math.ethz.ch 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.

Ingmar Visser
Department of Psychology, University of Amsterdam
Roetersstraat 15
1018 WB Amsterdam
The Netherlands
t: +31-20-5256735



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