[R-meta] A question about meta-regression Analysis

[Hamed Kianmehr]

I have some questions regarding the meta-regression analysis. I have the
database on the proportion (Below bubble plot). My advisor asked me to do
the polynomial regression. I have two questions:

1- Is it any polynomial regression pattern in this data?
2- I wrote below code but I couldn't get the line, Could you help me?
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res<-rma(yi=y, vi=s2, data=data, method="DL",mods = ~ poly(year, degree=2))
years <- 1989:2016
preds <- predict(res, transf = transf.ilogit, newmods =cbind(years,years^2))
wi <- 0.5/sqrt(data$s2)
wi <- 0.5 + 3.0 * (wi - min(wi))/(max(wi) - min(wi))
plot(data$year, transf.ilogit(y), cex=wi,xlab="Year",ylab="Patient
Expectation (%)")
lines(years, preds$pred)

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