The addpoly function can be used to add polygons, sometimes called ‘diamonds’, to a forest plot, for example to indicate summary estimates for subgroups of studies or to indicate fitted/predicted values based on models involving moderators.

addpoly(x, ...)



either an object of class "rma" or the values at which polygons should be drawn. See ‘Details’.


other arguments.


Currently, methods exist for two types of situations.

In the first case, object x is a fitted model coming from the rma.uni,, rma.peto, or rma.glmm functions. The model must either be a fixed- or random-effects model, that is, the model should not contain any moderators. The corresponding method is called addpoly.rma. It can be used to add a polygon to an existing forest plot (usually at the bottom), showing the summary estimate (with its confidence interval) based on the fitted model.

Alternatively, object x can be a vector with values at which one or more polygons should be drawn. The corresponding method is then addpoly.default.


Wolfgang Viechtbauer


Viechtbauer, W. (2010). Conducting meta-analyses in R with the metafor package. Journal of Statistical Software, 36(3), 1--48.

See also