On Sun, 12 Jun 2011, Jorge Ivan Velez wrote:
Hi Diviya,Take a look at the lrtest function in the lmtest package: install.packages('lmtest) require(lmtest) ?lrtest
Yes, when you have to nls() fits, say m1 and m2, you can do lrtest(m1, m2) However, I don't think that both m1 and m2 can be identified in y = a * exp(-(m1+m2) * x) + c Unless I'm missing something only the sum (m1+m2) is identified anyway. Best, Z
HTH, Jorge On Sun, Jun 12, 2011 at 1:16 PM, Diviya Smith <> wrote:Hello there, I want to perform a likelihood ratio test to check if a single exponential or a sum of 2 exponentials provides the best fit to my data. I am new to R programming and I am not sure if there is a direct function for doing this and whats the best way to go about it? #data x <- c(1 ,10, 20, 30, 40, 50, 60, 70, 80, 90, 100) y <- c(0.033823, 0.014779, 0.004698, 0.001584, -0.002017, -0.003436, -0.000006, -0.004626, -0.004626, -0.004626, -0.004626) data <- data.frame(x,y) Specifically, I would like to test if the model1 or model2 provides the best fit to the data- model 1: y = a*exp(-m*x) + c model 2: y = a*exp(-(m1+m2)*x) + c Likelihood ratio test = L(data| model1)/ L(data | model2) Any help would be most appreciated. Thanks in advance. Diviya [[alternative HTML version deleted]] ______________________________________________ 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.[[alternative HTML version deleted]] ______________________________________________ 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.
