> t-distribution with 402 df and a t-distribution with 2549 df so the > I would point out that there is effectively no difference between a > Models in S and S-PLUS" published by Springer. > The algorithm is described in Pinheiro and Bates (2000) "Mixed-effects > Why are the DF of Linf and K different? I would apreciate if you could point me to a reference > Nonlinear mixed-effects model fit by maximum likelihood > na.action= na.include, naPattern = ~!is.na(dLt)) > when runing nlme() on the following model: > So do I and I'm one of the authors of the package :-) > Hi, I' m having a hard time understanding the computation of degrees of freedom > On 1/27/06, gabriela escati peñaloza wrote: > Cc: R-help at > Emne: Re: how calculation degrees freedom > Fra: r-help-bounces at på vegne af Douglas Bates I don't think the "degrees of freedom police" would find that to be a The anova function could then print that "these p-values are large sample ones and hence only approximate". It could be nice, however, if anova() produced even an approximate anova table which can be obtained from Wald tests. > Along similar lines, I've noticed that the anova() function for lmer models now only reports the mean squares to go into the numerator but "nothing for the denominator" of an F-statistic probably in recognition of the degree of freedom problem. P-values the HPDinterval function from the coda package can create If you are interested in intervals rather than Posterior distribution of the parameters using Markov Chain MonteĬarlo sampling. > Of course, Monte Carlo p-values have their problems, but the world is not perfect.Īnother approach is to use mcmcsamp to derive a sample from the It is fairly fast to and takes about 10 lines of code to program. 2 log Q) in an empirical distribution based on simulations under the model that is to calculate a Monte Carlo p-value. So one way to "get around the problem" could be to evaluate the test statistic (e.g. simulate() is very fast - just like lmer(). > However, I'll just point out that for lmer models, there is a simulate() function which can simulate data from a fitted model. > Degrees of freedom for mixed models is a delicate issue - except in certain orthogonal designs. Next message: how calculation degrees freedom.Previous message: how calculation degrees freedom.How calculation degrees freedom Douglas Bates dmbates at
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