I tried : > test <- 0:10000 > test2 <- f(0:10000) > plot(test,test2) > plot(test,log(test2))
and > test <- seq(0,1,by=0.00001) > test2 <- sapply(test,f) > plot(test,log(test2)) > plot(test,test2) with the values you gave. And according to this result, you did nothing wrong. Zero is the only root of the function, as it is a monotone asymptotic to 0 for x>0, and not defined for negative x. Are you sure you're looking for the root of that function? Cheers Joris On Thu, Oct 15, 2009 at 11:18 PM, leohearn <leohe...@dal.ca> wrote: > > Hi > So, I have a dataset and I'm trying to solve for a parameter in an equation > using the dataset. Before applying more sophisticated statistical > techniques, I want to tell R to solve it out for each observation. I know I > have to use a loop for it (and I have done that before, but am a bit rusty), > but before I do that, I'm trying to get R to solve it for just one > observation, to make sure that I have that part right before applying to the > rest. However, when I do it, I get 0 for an answer, which is a valid answer, > but a trivial one. What am I doing wrong? (tips for the loop would also be > appreciated, but this is my main concern right now.) > > Here's my code: > f<-function(r){1-exp(-r*b)-(1/2)*(1-exp(-r*x1)+1-exp(-r*x2))} > uniroot(f,c(0,1))$root > > r is the unknown. I've plugged in a couple numbers from my data for b, x1, > and x2 such as: > b=5500 > x1=0.01 > x2=10000 > and > b=198000 > x1=10 > x2=500000 > and gotten 0 both times. > > Thanks in advance for your help. > -- > View this message in context: > http://www.nabble.com/Solving-an-equation-in-R-%28and-using-a-loop%29-tp25916187p25916187.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.