[R-sig-ME] Fitting linear mixed-effects models

Thierry Onkelinx th|erry@onke||nx @end|ng |rom |nbo@be
Wed Jan 26 17:01:11 CET 2022

Do you want a random effect for methionine source at the study level? That
could work with the alternative model you specified. However, that assumes
that you have multiple records for every combination of study and
methionine source. I would expect that you have only one record for each of
those combinations.

ir. Thierry Onkelinx
Statisticus / Statistician

Vlaamse Overheid / Government of Flanders
Team Biometrie & Kwaliteitszorg / Team Biometrics & Quality Assurance
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what the experiment died of. ~ Sir Ronald Aylmer Fisher
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ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey


Op di 25 jan. 2022 om 23:57 schreef Vinícius Carneiro de Souza <
vinicius2042 using hotmail.com>:

> I am trying to fit a linear model using the lmer function from data
> collected from literature from multiple studies.
> The response variable is the average daily gain of swine and the predictor
> is the different methionine sources in the different diets, which is a
> factor with 4 levels (4 different methionine sources)
> My original model is below, which includes a random intercept for study
> effect:
> #Z_ADG_g is the average daily gain
> #MM_Type_met is the methionine source factor
> #CO_Intra_Trial is the publication ID
> ADGmod <- lmer(Z_ADG_g~MM_Type_met+(1|CO_Intra_Trial), data=ErmDat3,
> weight=ADG_wt, REML = FALSE)
> summary(ADGmod)
> I would like to look what would be the effect of considering that each
> methionine source tested has a different/separate intercept. I was reading
> a book chapter from Bates et al. and found a table with some syntaxes that
> could work to specifying different intercepts for each methionine source,
> but it is not working. The model still has only one intercept.
> I tried the following model:
> ADGmod <-
> lmer(Z_ADG_g~MM_Type_met+(1|CO_Intra_Trial)+(1|CO_Intra_Trial:MM_Type_met),
> data=ErmDat3, weight=ADG_wt, REML = FALSE)
> summary(ADGmod)
> Does anyone know if it is even possible what I am trying to do?
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