[R-meta] margins command

Dear Patricia,

To start: 'sei = vi' looks wrong. Argument 'sei' is for passing the standard errors to the rma() function, but 'vi' sounds like a variable that contains sampling variances.

This aside, the answer to your question is yes. You can do this with: predict(res, newmods=c(1,1), intercept=FALSE).

As for marginal effects, you can use emmprep() together with the emmeans package (note that you will need to install the 'devel' version of metafor for this, since emmprep() was recent added; https://wviechtb.github.io/metafor/#installation).

An example:

library(metafor)

dat <- dat.bangertdrowns2004

res <- rma(yi, vi, mods = ~ wic + info, data=dat)
res

predict(res, newmods=c(1,1), intercept=FALSE)

sav <- emmprep(res)

library(emmeans)

emmeans(sav, specs="1", weights="proportional")

# this is identical to
predict(res, newmods = colMeans(model.matrix(res))[-1], digits=3)

# marginal means for 'wic' and 'info'
emmeans(sav, specs="wic", weights="proportional")
emmeans(sav, specs="info", weights="proportional")

If you do not want proportional weights, then just leave out the 'weights="proportional"' part.

Best,
Wolfgang

-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-project.org] On
Behalf Of Patricia Ziegelmann via R-sig-meta-analysis
Sent: Thursday, 09 March, 2023 14:17
To: r-sig-meta-analysis at r-project.org
Cc: Patricia Ziegelmann
Subject: [R-meta] margins command

Dear all,

I?m adjusting a simple metaregression model:

meta <- rma(yi = yi,
             sei = vi,
             mods = ~ risk1 + risk2,
             data = data1,
             method = "REML")

Both risk1 and risk2 are binary factors.

Is it possible to estimate a confidence interval for a function of the
fitted coefficients, let's say beta[1]+beta[2]?

Also, is there a command like the "margins" to have marginal effects
summaries?

Thanks in advance for any help,

Patricia

--
Patricia Klarmann Ziegelmann
Department of Statistics
Graduate Program in Epidemiology
Universidade Federal do Rio Grande do Sul (UFRGS)
http://lattes.cnpq.br/8486215358933890
Av. Bento Gon?alves, 9500 - Pr?dio 43-111 - Agronomia
91509-900 Porto Alegre - RS - BRAZIL