[R-meta] Choice of 'struct' in rma.mv inner| outer model

Hi all

I would like to learn what motivates the choice of  the variance structure
(struct parameter) in an inner|outer model set up in rma.mv. An example of
my test data is attached and I run rma.mv on my test data (dt) as below. In
my example below, some outer levels have only 1 inner level while other
have multiple inner levels. Any input on what should be considered when
choosing the model structure would be very helpful.

`res <- rma.mv(Effect_size, (Standard_error)^2, data = dt,
              random = ~ Dataset | Cohort, method="REML",
              control = list(optimizer="optim", optmethod="Nelder-Mead"))`

*Divya Ravichandar*
Scientist
Second Genome

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