 

Thank you Simon,  

that works well.  

I had tried previously 

m1 <-gamm(H ~ Tillage + s(Year, by =Tillage), random=list(Block=~ Tillage), na.action=na.omit, data =mydata, correlation = corARMA(form =~ Year|Tillage/Block, p = 1, q = 0))  

and that gave me convergence problems. 

Thank you!

eva 
Quoting Simon Wood:

> eva,
>
> The problem is that the random effects and correlation structure that 
> you have specified don't meet the restrictions required by lme (which 
> gamm calls). You can see this by trying
>
> M0 <-lme(H ~ Tillage , random=list(Block=~1), na.action=na.omit, data 
> = mydata, correlation = corARMA(form =~ Year|Tillage, p = 1, q = 0))
>
> which will fail because you have multiple observations of Year for 
> each level of Tillage, and because the random effect and correlation 
> formulae are incompatible.
>
> The multiple years problem could perhaps be solved by
>   corARMA(form =~ Year|Tillage/Block, p = 1, q = 0)
> if that makes modelling sense?
>
> A couple of possible fixes are then...
>
> M1 <-gamm(H ~ Tillage + s(Year, by =Tillage), 
> random=list(Tillage=~1,Block=~1), na.action=na.omit, data = mydata, 
> correlation = corARMA(form =~ Year|Tillage/Block, p = 1, q = 0))
>
> or, if you really don't want that r.e. structure, then
>
> M2 <-gamm(H ~ Tillage + s(Year, by =Tillage)+s(Block,bs="re"), 
> na.action=na.omit, data = mydata, correlation = corARMA(form =~ 
> Year|Tillage/Block, p = 1, q = 0))
>
> [I've assumed that the mapping between this message and the data you 
> sent off list is DepVar=H, Treatment=Tillage]
>
> best,
> Simon
>
>
> On 17/02/12 09:35, HERNANDEZ PLAZA, MARIA EVA wrote:
>>
>>
>> HELLO ALL,
>>
>> I AM GETTING AN ERROR MESSAGE WHEN TRYING TO RUN A GAMM MODEL LIKE 
>> THE ONE BELOW.
>>
>>  I AM USING R VERSION 2.14.1 (2011-12-22) AND MGCV 1.7-12.
>>
>> M1<-gamm(DepVar ~ Treatment + s(Year, by =Treatment), 
>> random=list(Block=~1), na.action=na.omit, data = mydata, correlation 
>> = corARMA(form =~ Year|Treatment, p = 1, q = 0))
>>
>> THIS IS THE ERROR MESSAGE
>>
>> Error in `*tmp*`[[k]] : attempt to select less than one element
>>
>> I have 312 observations. I get the error when I introduce the 
>> correlation structure in the model. I have the same problem even if 
>> I use /corAR1() /or I set bs=â€crâ€. I also tried to increase the 
>> number of iterations using the control option, but I find the same 
>> problem.
>>
>> Is there any other way in which I could include the correlation structure?
>>
>> I would appreciate any suggestions
>>
>> thanks!
>>
>> eva
>>         [[alternative HTML version deleted]]
>>
>>
>>
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>
> -- 
> Simon Wood, Mathematical Science, University of Bath BA2 7AY UK
> +44 (0)1225 386603               http://people.bath.ac.uk/sw283
>
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