[R-meta] Issues when using rma.mv
||@t@ @end|ng |rom dewey@myzen@co@uk
Sat May 20 15:23:39 CEST 2023
If you have all the raw data why do you not just analyse this as a
multi-level mode (or mixed effects model)? Perhaps I have misunderstood
Incidentally your mailer is set to send HTML so your post is mangled
since this is a plain text list.
On 19/05/2023 17:03, Diego Gallego García via R-sig-meta-analysis wrote:
> Good morning,
> First post here, so I apologize if I do not explain my issue in the
> best way.
> I am currently conducting a review on the length of the dependence period
> (time that the nestling spends with parents) in birds. I want to test which
> ecological factors affect this variable.
> My raw dataset has one row per species and per study (i.e., there are some
> studies which account for more than one species, so I separate each species
> studied in each research), with its corresponding variables of the
> dependence period (PD: days), SD, N (number of individuals studied), etc...
> My raw dataset should look like this (dummy data):
> Study_ID Species Latitude Body weight Status
> DP N SD
> 1 A 50 3.4
> Resident 45 3 1.81
> 2 A 38 3.4
> Migrant 32 1 N/A
> 2 B 43 2.1
> Migrant 33 11 3.45
> 3 B 38 2.1
> Resident 38 6 2.45
> 3 C 12 3.6
> Resident 159 2 0
> Now, as you may see, there are some studies with an n=1 (only one
> individual was examined), so there is no valid SD for the study (i.e.,
> N/A). Thus, for the escalc() formula, I should delete them. But what about
> the last example? There were two individuals studied in that paper, and
> both yielded the same result, so the SD is roughly 0.
> Afterwards, when using rma.mv for a mixed-effects model, those studies with
> SD=0 (then vi=0) are giving me problems. Specifically, there are some
> warnings in my models:
> Warning messages:
> 1: There are outcomes with non-positive sampling variances.
> 2: 'V' appears to be not positive definite.
> The model is the following:
> p1 <- rma.mv(data$yi, data$vi, mods= ~Latitude*Status,
> random=~1|Species, data=data)
> Should I be worried about these warnings? Any way to fix them?
> I appreciate any help.
> *MSc Diego Gallego García*
> Proyecto Águila del Chaco - Chaco Eagle Project
> Center for the Study and Conservation of Raptors in Argentina *(CECARA)*
> Institute of Earth and Environmental Sciences of La Pampa *(INCITAP)*
> National Scientific and Technical Research Council *(CONICET)*
> diegothen using gmail.com
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> R-sig-meta-analysis mailing list @ R-sig-meta-analysis using r-project.org
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