Feature request: paired forest/risk-of-bias plot

[mcguinlu]

Problem The most recent paper on ROB2, and indeed the Cochrane Handbook itself, suggest presenting risk-of-bias information as part of a paired forest plot. Risk-of-bias assessments are intended to be result-specific, and so presenting information about the potential bias in a result alongside the main analysis helps to ensure that the results are interpreted appropriately. The paired figure from the ROB2 paper is below, for reference:

This plot is something that has been requested by other users and has been on the cards for a while:

Somebody should glue this to robvis to make figures like pic.twitter.com/K87V6HWQdW

— Paul Sharpe (@PaulSharpeY) September 14, 2020

Until recently, I was not sure how to do it, as the metafor::forest() function is quite restrictive in terms of matching with anything else, and aligning text tables in ggplot2 is a pain. However, @rdboyes recently shared code for producing a beautiful forest plot to Twitter. The code is available here: https://github.com/rdboyes/Forest_plot_with_table/blob/master/create_figure.R

Describe the solution you'd like Ideally, I'd like to add a function (rob_blobbogram()) to robvis which creates these table/forest-plots/risk-of-bias plots.

The function would take two main inputs:

• The output of a meta-analysis (e.g. an rma object from metafor::rma())
• A risk-of-bias summary table in the same format as when passing to other rob_*() functions (for consistency)

Plus then some styling arguments, similar to the other rob_*() functions.

Describe alternatives you've considered I have looked at packages like patchwork and cowplot to see if two disctinct plots could be aligned easily. It is possible - however ggplot2 is not great at handling text/tables. So while the forest plot and risk-of-bias plots could be aligned, adding the extra tables describing the study's results proved difficult.

Predicted issues One important issue is that when previewing the plot created by @rdboyes, it looks scewy in the RStudio viewer but perfect once saved to a file. From a user interface point of view, this will cause a lot of issues as people email to say the graph looks wrong. I think it should be possible to address this by setting the dimensions of the RStudio viewer panel, but I haven't looked into it a whole lot. Perhaps @rdboyes, you might know?

Secondly, the current code for the forest-plot draws from a table rather than a meta-analysis object, and also does not include other aspects produced by the meta-analysis such as overall summaries or heterogeneity. However, by adding rows containing these, it should be possible to adapt the existing code to work.

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Practical issues

@AJFOWLER - are you interested in having a go at this, as it might be a bit more interesting/challenging for you than refactoring the current code base?

@rdboyes - are you happy for us to reuse your forest plot code here/be involved in developing this functionality?