Dear all,

I have one Model (M3) fitted using the lme package, and I have  
checked the correlation structure of within-group errors using

plot(ACF (M3,maxLag=10),alpha=0.05)

But now I am not sure how to interpret this plot for the empirical  
autocorrelation function.

The problem is that I am used to see/interpret diagrams in which all  
the autocorrelation Lags, except lag-1, are inside the confidence  
envelopes, or those plots where only Lags 1 and 2 are outside those  
envelopes.

But how should I interpret my ACF plot, where Lags 1, 7, 8 and 9, are  
those outside those envelopes?

Is there any correlation structure?
Which one might that be? AR1()?


Also, I have used the plot of the empirical ACF of the normalized  
residuals, but it gives exactly the same results.

Could you please help me?

Best regards
Sara Mouro


Sara Maltez Mouro

Centro de Ecologia Funcional
Departamento de Botânica
Universidade de Coimbra

sara@gmesintra.com
www.uc.pt/ecology/saramaltezmouro


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