[R-sig-ME] double repeated measures

Dexter Locke dexter.locke at gmail.com
Thu Aug 10 15:06:00 CEST 2017


While this doesn't address the question about repeated measures, consider
looking at

O’Hara, R. B., Kotze, D. J., O ’Hara, R. B., & Kotze, D. J. (2010). Do not
log-transform count data. Methods in Ecology and Evolution, 1(2), 118–122.

for the left-hand side of the model.

- Dexter

On Wed, Aug 9, 2017 at 10:52 PM, Julie McIntyre <jpmcintyre at alaska.edu>

> Hello,
> I am trying to fit a model to data that are recorded in a doubly-repeated
> measures type design, and I'm having trouble with the syntax for lmer.  The
> response is a count representing the number of animals harvested at each of
> six locations during a hunting season.  Counts are recorded daily at each
> location for a fixed period (about 45 days).  In addition, the daily counts
> at each location have been repeated themselves over several years (about
> 30).  The dates of the counts are the same every year.  Additional
> covariates are measured on a daily basis.
> Graphically, for all locations there is a clear trend in count by day, with
> some year-to-year variation.  There are also clear but weaker trends in
> counts by year (for fixed day), with variation among locations.  The
> general shape of the trend changes quite a bit depending on the day (e.g.,
> early vs. late in the season).  That said, the main interest is in
> understanding the influence of the covariates on harvest.
> I believe the following code fits a random intercept and slope model to
> daily counts within years, separately for each location.  This model fits
> well, and allows testing of the covariate effects (X1 and X2).  However it
> ignores the second layer of repetition and the trend in count by year,
> within locations.
> M1=lmer(log(Count+1)~X1+X2+Location+Day+(1+Day|Year), data=Harvest)
> I would like to know the correct syntax to also include terms for the
> repeated measurement by year, within locations.  This model might be close,
> but I'm just not certain:
> M2=lmer(log(Count+1)~X1+X2+Day+(1+Day|Year/Location)+(1+Year|Location),
> data=Harvest)
> I'd appreciate any suggestions or advice.  Thank you!
> Julie McIntyre
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