>
>
> >
> Please suggest how to define subset in my case
>
> How would I know? I still haven't seen your data. You seem to be
> mistaken on what is and is not included in your model and you fitted it.
> What hope do we have...? However, given the model 'mig.stds' from above
> in this email:
>
> > 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()
>
> If you want to consider dredged models containing temp_max, then you
> would do
>
> dredge(mig.stds, subset = temp_max)
>
> If you want models that contain temp_max and coast, then you'd do
>
> dredge(mig.stds, subset = temp_max & coast)
>
> or
>
> dredge(mig.stds, fixed = ~ temp_max + coast)
>
> The bits you include in subset or fixed are the names of your variables
> that you want in or out of the models. In your case, the names of the
> variables as input into the model formula. With 'subset' you need to use
> logical operators (and [&], or [|]) whilst with 'fixed' you can specify
> a formula of variables that should be included or excluded in the same
> way you'd write any R formula.
>
> But, now having been told this, please note that this is *all* discussed
> on the ?dredge help page if you bother to read it. I've never used this
> package, and, OK, I have used R for going on for 11 or 12 years now so
> am used to reading help pages and understand the language a bit more you
> perhaps do, but you do seem to be asking questions or running into
> problems that are all covered by the help pages.
>
> => I posted it for help, after following the manual with the command dredge
> but receiving an error message two days ago.
>
> command target<-dredge(mig.stds, subset = temp_max)
>
error in eval(expr, envir, enclos) : 'temp_max' not found
One possible cause could be data = datam.std.
datam.std was produced as the code below, which seemed to make it hard to
find explanatory variables.
Please kindly share your experience in R, because I am unsure if my
assumption is logical or not.
Also, please kindly advise how to modify the command for dredging subset if
possible.
( command target<-dredge(mig.stds, subset = temp_max))
Thank you in advance.
Elaine
code
library(MuMIn)
datam <-read.csv("c:/migration/Mig_ratio_20100817.csv",header=T,
row.names=1)
# std regression model (16 indep. variables)
datam.sd<-scale(datam)
datam.std<-as.data.frame(datam.sd)
summary (datam.std)
mean(datam.std)
# obtain standard deviation
sd(datam.std)
mig.stds
<-lm(SummerM_ratio~temp_ran+temp_mean+temp_max+temp_min+evi_ran+evi_mean+evi_max+evi_min+prec_ran+prec_mean+prec_max+prec_min+topo_var+topo_mean+coast+Iso_index_0808,data=datam.std)
summary(mig.stds)
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