[R-sig-ME] Time-varying random effects

[Thierry Onkelinx]

Hi Mark,

I have some questions on the design.
- Can you identify the individual pigs in the data?
- How is the grouping of the pigs? Is it constant (e.g. all pigs from the
same litter stay together)? Or does the grouping changes over time?
- Do expect any effect of the pens itself? Or are the pens rather a just
group of pigs.

Best regards,

Thierry

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to say
what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

2016-11-23 15:58 GMT+01:00 Marc Jacobs <marc.jacobs012 op gmail.com>:

> Hi,
>
>
>
> By request of Prof. Bolker, i am posting my question here.
>
>
> I am currently in the process of analyzing a growth model in pigs. Due to
> the confidentiality of the data, I cannot add any data which is of course
> the preferred course, but I hope to gain some insight here. I apologize in
> advance if the description is unclear.
>
>
>
> The data shows growth in 300+ pigs over 168 days, measured on 11
> time-points. These 168 days can be divided in three separate phases:
> farrowing/mom (2 timepoints), nursery (4 timepoints), and growth-finish (5
> timepoints).
>
>
>
> During each of these phases, the animals are placed in different rooms and
> pens (nested in the rooms), which by definition are random factors. Also,
> there is a genetic dependency of pigs (litter) nested in moms, which would
> be a crossed effect, since the effect takes place across the entire
> dataset, separate from the room/pen (pigs are separated from the litter
> after the farrowing/mom phase).
>
>
>
> As such, from my point of view, the room/pen are now time-varying random
> effects. Since I wish to model the entire growth curve, I was wondering if
> anybody knows how to incorporate time-varying random effects?
>
>
>
> My gut feeling tells me this is quite easy, but my models do not converge.
>
>
>
> If you need more information, please let me know.
>
>
>
> Marc
>
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