[R-sig-ME] unreplicated repeated measures

[Jinsong Zhao]

An artificial data:

  Trt     Time          Yield
    1     1983     -1.3249564
    1     1986      0.7196249
    1     1993      0.1483918
    1     1998      0.1739599
    1     2003     -0.5962691
    1     2010     -0.1382644
    2     1983     -0.5212350
    2     1986     -0.5751201
    2     1993     -0.7656928
    2     1998      1.0399397
    2     2003      1.5328539
    2     2010     -0.5204021
    3     1983      0.9821412
    3     1986     -0.4376944
    3     1993     -1.2453136
    3     1998     -0.3852303
    3     2003     -1.9200383
    3     2010      0.2154259

Thanks again for your attention.

Regards,
Jinsong

On 2011-11-23 23:33, Jinsong Zhao wrote:
> It's a old post found by searching.
>
> On 2009-6-24 1:29, Christine Griffiths wrote:
>> Dear R users,
>>
>> Sorry if this question is not applicable to this site. I am having
>> problems
>> analysing unreplicated repeated measures. I calculated food web
>> properties
>> for three treatments over time (10 months). It is unreplicated in that I
>> only have one observation per month per treatment. My problem is that
>> I am
>> interested in how a food web property varies between Treatments and over
>> time.
>>
>
> I have a similar data set, and hope to do similar statistical analysis.
>
>> Originally I had tried using lmer:
>> m4<-lmer(lncon~Treatment*month+(1|month),data=dataset)
>> but this provides the following error for which I have not found an
>> explanation to on the R site.
>> Error in mer_finalize(ans) : Calculated PWRSS for a LMM is negative
>
> gls() in nlme package was recommended to deal with my situation.
> However, I don't know how to describe the fixed effects:
>
> gls(lncon~Treatment*month, data = dataset)
>
> or
>
> gls(lncon~Treatment+month, data = dataset)
>
> It seems that the above two formula can run correctly, however, I don't
> know which one should be preferred, and whether the variable month
> should be treated as a factor or a continuous variable. I have read the
> book of Pinheiro & Bates, and found the time variable in dataset, e.g.,
> Orthodont, is a numeric vector. What's the difference?
>
> Is it possible to intercept the data by lme() or lmer(), for there is no
> group variable?
>
> <snip>
>
> Any suggestions or comments will be really appreciated. Thanks in advance.
>
> Regards,
> Jinsong
>
> _______________________________________________
> R-sig-mixed-models at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>