I already ran a mixed model and got convergence. I have 700 data points. Now, I am running a new mixed model that adds the ARMA (corARMA) covariance pattern. I keep getting an error message telling me that the model did not reach convergence. I already tried reducing my tolerance to 1e-1 and increased the number of iterations to 7,000. Still, I am not having any luck. Any suggestions to get my model to work properly so I can get my parameter estimates? I pasted my covariance code below. LVB2.nlme<-update(LVB.nlme, corr=corARMA(p=1, q=1), control=nlmeControl(maxIter=6000, tolerance=1e-1, msVerbose=TRUE))
Mike, Specifying starting values for the AR and MA parameters inside the corARMA function will help. You can use the ACF to choose decent starting values. Keep in mind that the correlation is imposed inside your random effect. Alain ------------
_______________________________________________ R-sig-mixed-models mailing list R-sig-mixed-models at r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models End of R-sig-mixed-models Digest, Vol 55, Issue 11 **************************************************
Dr. Alain F. Zuur First author of: 1. Analysing Ecological Data (2007). Zuur, AF, Ieno, EN and Smith, GM. Springer. 680 p. URL: www.springer.com/0-387-45967-7 2. Mixed effects models and extensions in ecology with R. (2009). Zuur, AF, Ieno, EN, Walker, N, Saveliev, AA, and Smith, GM. Springer. http://www.springer.com/life+sci/ecology/book/978-0-387-87457-9 3. A Beginner's Guide to R (2009). Zuur, AF, Ieno, EN, Meesters, EHWG. Springer http://www.springer.com/statistics/computational/book/978-0-387-93836-3 Other books: http://www.highstat.com/books.htm Statistical consultancy, courses, data analysis and software Highland Statistics Ltd. 6 Laverock road UK - AB41 6FN Newburgh Tel: 0044 1358 788177 Email: highstat at highstat.com URL: www.highstat.com URL: www.brodgar.com