10.2 Summary plots

10.2.1 Basics

Once we have successfully imported the risk of bias summary table into R, creating the risk of bias figures is quite straightforward.

To get started, a simple weighted summary barplot using the ROB2 example dataset (data_rob2) is created by running the following code:

rob_summary(data = data_rob2, tool = "ROB2")

10.2.2 Modifying your summary barplot

The rob_summary() function has the following parameters:

Argument Description
data A dataframe containing summary (domain) level risk-of-bias assessments, with the first column containing the study details, the second column containing the first domain of your assessments, and the final column containing a weight to assign to each study. The function assumes that the data includes a column for overall risk-of-bias. For example, a ROB2.0 dataset would have 8 columns (1 for study details, 5 for domain level judgments, 1 for overall judgments, and 1 for weights, in that order).
tool The risk of bias assessment tool used. RoB2.0 (tool=‘ROB2’), ROBINS-I (tool=‘ROBINS-I’), and QUADAS-2 (tool=‘QUADAS-2’) are currently supported.
overall An option to include an additional bar for overall risk-of-bias in the figure. Default is FALSE.
weighted An option to specify whether weights should be used in the barplot. Default is TRUE, in line with current Cochrane Collaboration guidance.
colour An argument to specify the colour scheme for the plot. Default is ‘cochrane’ which used the ubiquitous Cochrane colours, while a preset option for a colour-blind friendly palette is also available (colour = ‘colourblind’).
quiet A logical option to quietly produce the plot without displaying it. Default is FALSE.

Examples of the functionality of each argument are described below.

10.2.2.1 Tool

An argument to define the tool template you wish to use. In the example above, the ROB2 template is used. The two other primary templates - the ROBINS-I and QUADAS-2 templates - are demonstrated below:

rob_summary(data = data_robins, tool = "ROBINS-I")

rob_summary(data = data_quadas, tool = "QUADAS-2")

10.2.2.2 Overall

By default, an additional bar representing the overall risk of bias judgments is not included in the plot. If you would like to include this, set overall = TRUE. For example:

rob_summary(data = data_rob2, tool = "ROB2", overall = TRUE)

10.2.2.3 Weighted or un-weighted bar plots (weighted)

By default, the barplot is weighted by some measure of study precision, so that the barplot shows the proportion of information rather than the proportion of studies that is at a particular risk of bias. This approach is in line with the Cochrane Handbook.

You can turn off this option by setting weighted = FALSE to create an un-weighted barplot. For example, compare the following two plots:

rob_summary(data = data_rob2, tool = "ROB2")

rob_summary(data = data_rob2, tool = "ROB2", weighted = FALSE)

10.2.2.4 Colour scheme (colour)

NB: Please note the non-US English spelling of colour

The colour argument of both plotting functions allows users to select from two predefined colour schemes, “cochrane” (default) or “colourblind”, or to define their own palette by providing a vector of hex codes.

For example, to use the predefined “colourblind” palette:

rob_summary(data = data_rob2, tool = "ROB2", colour = "colourblind")

And to define your own colour scheme:

rob_summary(data = data_rob2, tool = "ROB2", colour = c("#f442c8","#bef441","#000000"))

When defining your own colour scheme, you must ensure that the number of discrete judgments (e.g. “Low”/“Moderate”/“High”/“Critical”) and the number of colours specified are the same. Additionally, colours must be specified in order of ascending risk-of-bias (e.g. “Low” -> “Critical”), with the first hex corresponding to “Low” risk of bias.

10.2.3 Saving your plot

See Section 10.5 for detailed instructions on how to save your plot.



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