Plot Method for 'cumul.rma' Objects

Plot method for objects of class "cumul.rma".

# S3 method for cumul.rma
plot(x, yaxis, xlim, ylim, xlab, ylab,
     at, transf, atransf, targs, digits, cols=c("gray80","gray10"),
     grid=TRUE, pch=19, cex=1, lwd=2, ...)

Arguments

x	an object of class "cumul.rma".
yaxis	either "tau2", "I2", or "H2" to indicate what values should be placed on the y-axis. See ‘Details’.
xlim	x-axis limits. If unspecified, the function tries to set the x-axis limits to some sensible values.
ylim	y-axis limits. If unspecified, the function tries to set the y-axis limits to some sensible values.
xlab	title for the x-axis. If unspecified, the function tries to set an appropriate axis title.
ylab	title for the y-axis. If unspecified, the function tries to set an appropriate axis title.
at	position of the x-axis tick marks and corresponding labels. If unspecified, the function tries to set the tick mark positions/labels to some sensible values.
transf	optional argument to specify a function that should be used to transform the summary estimates (e.g., transf=exp; see also transf). If unspecified, no transformation is used.
atransf	optional argument to specify a function that should be used to transform the x-axis labels (e.g., atransf=exp; see also transf). If unspecified, no transformation is used.
targs	optional arguments needed by the function specified via transf or atransf.
digits	integer to specify the number of decimal places to which the tick mark labels of the x- and y-axis should be rounded. Can also be a vector of two integers, the first to specify the number of decimal places for the x-axis, the second for the y-axis labels (e.g., digits=c(2,3)). If unspecified, the function tries to set the argument to some sensible values.
cols	vector with two or more colors to use for visualizing the order of the cumulative results.
grid	logical to specify whether a grid should be added to the plot (can also be a color name).
pch	plotting symbol to use. By default, a filled circle is used. See points for other options.
cex	symbol expansion factor.
lwd	line width.
...	other arguments.

Details

The function can be used to visualize the results from a cumulative meta-analysis as obtained with the cumul function.

The plot shows the model estimate (i.e., the estimated overall/average outcome) on the x-axis and some measure of heterogeneity on the y-axis in the cumulative order of the results in the "cumul.rma" object. By default, \(\tau^2\) is shown on the y-axis for a random-effects model and \(I^2\) otherwise, but one can also use argument yaxis to specify the measure of heterogeneity to place on the y-axis.

The color gradient of the points/lines indicates the order of the cumulative results (by default, light gray at the beginning, dark gray at the end). A different set of colors can be chosen via the cols argument. See ‘Examples’.

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

See also

cumul.rma.uni

Examples

### calculate log risk ratios and corresponding sampling variances
dat <- escalc(measure="RR", ai=tpos, bi=tneg, ci=cpos, di=cneg, data=dat.bcg)

### random-effects model
res <- rma(yi, vi, data=dat)

### cumulative meta-analysis (in the order of publication year)
sav <- cumul(res, transf=exp, order=dat$year)

### plot of model estimate and tau^2 over time
plot(sav)

### illustrate some other plot options
plot(sav, yaxis="I2", ylim=c(0,100), atransf=exp, at=log(seq(1.3, 1.6, by=.1)),
     lwd=5, cex=1.5, cols=c("green","blue","red"))