Nested and crossed random effects
I predict you will receive constructive feedback if you provide a dataframe with (simulated) data. Reinhold Kliegl
On Thu, Jul 30, 2009 at 5:09 AM, Patrick Onyango<pogola at princeton.edu> wrote:
Dear All, I am in transition from SPSS to R and so I am trying to read as much as I can to address some of my immediate statistical needs. And so, as with most transitions, I am plagued by haste that some of you may find quite sublime; but I ask for leniency. I am trying to model a response variable, response, ?as a function of the following fixed terms: a, b, c, d, and e; and 3 random effects: f, g, h such that g denotes the ID of my sampling subjects sampled over time and the subjects are distributed in 5 groups, here denoted by f. An important note is that I sampled g as part of a pair with h such that overall I have 131 samples involving 39 different gs and 45 different hs where h may be or may not be at 2 levels of two of the fixed terms, let's for convenience call those terms d and e, each with levels 1 and 2. The number of samples among h are pretty uneven. The main idea is to find out what g does given the level of h; and how is that influenced by a,b,c as well as vary by the IDs f,g,h where f is the highest level of random effects and g and h should probably be crossed terms? This is what I did: model<-lmer(response~a+b+c+d+e+(1|f)+(1|f/g)+(1|g)+(1|h), method='ML') but got the following warning message Error: length(f1) == length(f2) is not TRUE In addition: Warning messages: 1: In g:f: ?numerical expression has 131 elements: only the first used 2: In g:f: ?numerical expression has 131 elements: only the first used 3: In h:f : ?numerical expression has 131 elements: only the first used 4: In h:f : ?numerical expression has 131 elements: only the first used Then I tried model<-lmer(response~a+b+c+d+e+(1|f)+(1+f|g)+(1|g)+(1|h), method='ML') only making one change at the nested term; and got the following Error message In mer_finalize(ans) : singular convergence (7) Further, the output from the latter call found a perfect correlation for the intercept and slope of g indicating overparametization; and so I sought to simplify the model by removing the correlation term and assuming homoscedasticity for g in respect to f by replacing the nested term in the previous call with (1|f:g), and also adding corr = FALSE in the call But got the following Error: length(f1) == length(f2) is not TRUE I go in your records as probably having the longest post. An achievement indeed. I need and will be most thankful for help in figuring how to handle my data and in deciphering the error messages. Many thanks in advance; and please let me if further clarifications would suffice. Patrick
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