[R] How to get slope estimates from a four parameter logistic with SSfpl?

Is the following helpful? pdd-deriv(~a+(b-a)/(1+exp((c-t)/d)),d) pdd expression({ .expr1 - b - a .expr2 - c - t .expr4 - exp(.expr2/d) .expr5 - 1 + .expr4 .value - a + .expr1/.expr5 .grad - array(0, c(length(.value), 1L), list(NULL, c(d))) .grad[, d] - .expr1 *

Re: [R] How to get slope estimates from a four parameter logistic with SSfpl?

Yes that worked perfectly. Many thanks. From: Peter Ehlers [ehl...@ucalgary.ca] Sent: 19 October 2009 19:17 To: Weber, Sam Cc: r-help@R-project.org Subject: Re: [R] How to get slope estimates from a four parameter logistic with SSfpl? Weber, Sam wrote:

[R] How to get slope estimates from a four parameter logistic with SSfpl?

Hi, I was hoping to get some advice on how to derive estimates of slopes from four parameter logistic models fit with SSfpl. I fit the model using: model-nls(temp~SSfpl(time,a,b,c,d)) summary(model) I am interested in the values of the lower and upper asymptotes (parameters a and b), but

Re: [R] How to get slope estimates from a four parameter logistic with SSfpl?

Weber, Sam wrote: Hi, I was hoping to get some advice on how to derive estimates of slopes from four parameter logistic models fit with SSfpl. I fit the model using: model-nls(temp~SSfpl(time,a,b,c,d)) summary(model) I am interested in the values of the lower and upper asymptotes