[R-meta] Error Stopped because k = 0 after sub setting​.

[Klaow sota]

I have some problems with analysis in subgroup
It showed this message:
 > # fit random-effects model in the three subgroups
> res.s <- rma(yi, vi, subset=(interven=="PZQ"),data=dat)
Error: Stopped because k = 0 after sub setting​.

How should I fix it?
Is it caused from vi, yi?

Best regards,
Klaow

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