Re: [R] Find position of asymptote

2012-04-20 Thread Petr Savicky
On Thu, Apr 19, 2012 at 03:12:34PM -0800, Katrina Bennett wrote: > Dear R Help, > > Sorry I wasn't more clear before. Here is another crack at this. > > What I am still trying to do is estimate the point on a line when the > slope changes or asymptotes. I have found some similar postings > talkin

Re: [R] Find position of asymptote

2012-04-19 Thread Bert Gunter
Katrina: > > Is there a better way to then pick off the change points or find the > asymptotes of a function in R? Basic calculus? (if parametrically specified). Otherwise, probably best to consult your local statistician (or maybe a numerical analyst). -- Bert > > Thank you. > > Katrina > >

Re: [R] Find position of asymptote

2012-04-19 Thread Katrina Bennett
Dear R Help, Sorry I wasn't more clear before. Here is another crack at this. What I am still trying to do is estimate the point on a line when the slope changes or asymptotes. I have found some similar postings talking about this but no answers. https://stat.ethz.ch/pipermail/r-help/2003-Januar

Re: [R] Find position of asymptote

2012-04-19 Thread Katrina Bennett
Hi David, thanks for the reply. This is not a homework problem, although it may sound like one :) I was trying to provide a reproducible example of what I am trying to do. The problem is something I am trying to work on for my PhD program. I've been using the nls() function to derive a self-start

Re: [R] Find position of asymptote

2012-04-19 Thread David Winsemius
On Apr 19, 2012, at 4:41 AM, Katrina Bennett wrote: Hi all, I would like to find the x position of an two asymptotes. Here is a sample of what I would like to do: x <- seq(1, 153,, 153) a <- 85 m <- 65 s =-1.5 fn <- function (x, a, m, s) { a * (exp((m - x)/s) * (1/s))/((1 + exp((m - x)/s)))^

[R] Find position of asymptote

2012-04-19 Thread Katrina Bennett
Hi all, I would like to find the x position of an two asymptotes. Here is a sample of what I would like to do: x <- seq(1, 153,, 153) a <- 85 m <- 65 s =-1.5 fn <- function (x, a, m, s) { a * (exp((m - x)/s) * (1/s))/((1 + exp((m - x)/s)))^2 } plot.deriv1 <- fn(1:153, a, m, s) I can find the mi