addpoly.RdFunction to add polygons (sometimes called ‘diamonds’) to a forest plot, for example to show pooled estimates for subgroups of studies or to show fitted/predicted values based on models involving moderators.
addpoly(x, ...)Currently, methods exist for three types of situations.
In the first case, object x is a fitted model coming from the rma.uni, rma.mh, rma.peto, rma.glmm, or rma.mv functions. The model must either be an equal- or a random-effects model, that is, the model should not contain any moderators. The corresponding method is addpoly.rma. It can be used to add a polygon to an existing forest plot (usually at the bottom), showing the pooled estimate (with its confidence interval) based on the fitted model.
Alternatively, x can be an object of class "predict.rma" obtained with the predict function. In this case, polygons based on the predicted values are drawn. The corresponding method is addpoly.predict.rma.
Alternatively, object x can be a vector with the values at which one or more polygons should be drawn. The corresponding method is addpoly.default.
Viechtbauer, W. (2010). Conducting meta-analyses in R with the metafor package. Journal of Statistical Software, 36(3), 1–48. https://doi.org/10.18637/jss.v036.i03
addpoly.rma, addpoly.predict.rma, and addpoly.default for the specific method functions.
forest for functions to draw forest plots to which polygons can be added.