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, ...)

## Arguments

x

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

...

other arguments.

## Details

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 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, x can be an object of class "predict.rma" obtained with the predict.rma 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 values at which one or more polygons should be drawn. The corresponding method is then addpoly.default.

## Author

Wolfgang Viechtbauer wvb@metafor-project.org https://www.metafor-project.org

## References

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.rma and forest.default for functions to draw forest plots to which polygons can be added.