Thank you.
Most of the answers solved the puzzles.

Q2


> > I tried to display sub-model with only temp_ran using the code below but
> > failed.
> > Please kindly suggest the potential failure cause.
> >
> > code
> >
> > library(MuMIn)
> > datam <-read.csv("c:/migration/Mig_ratio_20100817.csv",header=T,
> > row.names=1)
>
>
> mig.stds <-lm(SummerM_ratio ~ temp_max + evi_mean + topo_var +
>              topo_mean + coast + Iso_index_0808,
>              ## now tell R were to find the variables in formula
>              data = datum.std)
> ## If you are fitting a Gaussian GLM it is better fitted with lm()
>

 => Please explain why fitted lm is better for GLM.

>
>
>
> But temp_ran is not in your model...
>
> > error in eval(expr, envir, enclos), 'temp_ran' not found
>
> When used properly (none of this datam.std$ business), subset will do
> what you want:
>
> > dd2 <- dredge(lm1, subset = X1)
> > dd2
> Global model: lm(formula = y ~ ., data = Cement)
> ---
> Model selection table
>    (Int)        X     X1     X2      X3      X4 k   R.sq Adj.R.sq     RSS
> 3   52.58          1.4680 0.6623                 4 0.9787   0.9744   57.90
>
> => Please suggest how to define subset in my case

Finally, it would be highly appreciated to recommend any references of R for
a beginner like me.


Elaine

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