[R] linear mixed model using lmer

[Jeff Newmiller]

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On March 4, 2022 4:41:57 PM PST, array chip via R-help <r-help using r-project.org> wrote:
>Dear all, I have this simple dataset to measure the yeild of a crop collected in 2 batches (attached). when I ran a simple inear mixed model using lmer to estimate within-batch and between-batch variability, the between-batch variability is 0. The run showed that data is singular. Does anyone know why the data is singular and what's the reason for 0 variability? is it because the dataset only has 2 batches?
>> daty<-read.table("datx.txt",sep='\t',header=T,row.names=NULL)
>> library(lme4)> lmer(yield~1+(1|batch),daty)
>boundary (singular) fit: see ?isSingular
>Linear mixed model fit by REML ['lmerMod']
>Formula: yield ~ 1 + (1 | batch)
>   Data: daty
>REML criterion at convergence: 115.6358
>Random effects:
> Groups   Name        Std.Dev.
> batch    (Intercept) 0.000   
> Residual             2.789   
>Number of obs: 24, groups:  batch, 2
>Fixed Effects:
>(Intercept)  
>      5.788  
>
>Thanks!
>John
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