meta (version 0.5)

funnel: Plot to assess funnel plot asymmetry

Description

Draw a funnel or radial plot to assess funnel plot asymmetry in the active graphics window.

Usage

funnel(x, y, xlim=NULL, ylim=NULL, xlab=NULL, ylab=NULL,
       comb.f=FALSE, axes=TRUE, labels=NULL, cex.lab=0.8,
       log="", yaxis="se", sm=NULL, ...)
radial(x, y, xlim=NULL, ylim=NULL,
       xlab="Inverse of standard error",
       ylab="Standardised treatment effect (z-score)",
       comb.f=TRUE, axes=TRUE, labels=NULL, cex.lab=0.8,
       level=NULL, ...)

Arguments

x

An object of class meta, or estimated treatment effect in individual studies.

y

Standard error of estimated treatment effect (mandatory if x not of class meta).

xlim

The x limits (min,max) of the plot.

ylim

The y limits (min,max) of the plot.

xlab

A label for the x axis.

ylab

A label for the y axis.

comb.f

A logical indicating whether the pooled fixed effects estimate should be plotted.

axes

A logical indicating whether axes should be drawn on the plot.

labels

A character string specifying the text to be used as plotting symbol.

cex.lab

The magnification to be used for x and y labels.

log

A character string which contains "x" if the x axis is to be logarithmic, "y" if the y axis is to be logarithmic and "xy" or "yx" if both axes are to be logarithmic (applies only to function

yaxis

A character string indicating which type of weights are to be used. Either "se", "inv", or "size" (applies only to function funnel).

sm

A character string indicating underlying summary measure, e.g., "RD", "RR", "OR", "WMD", "SMD" (applies only to function funnel).

level

The confidence level utilised in the plot (applies only to function radial).

...

Graphical parameters as in par may also be passed as arguments.

Details

A funnel plot or radial plot, also called Galbraith plot, is drawn in the active graphics window. If comb.f is TRUE, the pooled estimate of the fixed effects model is plotted. If level is not NULL, the corresponding confidence limits are drawn.

In the funnel plot, if yaxis is "se", the standard error of the treatment estimates is plotted on the y axis which is likely to be the best choice (Sterne & Egger, 2001). Other possible choices for yaxis are "inv" (inverse of the variance) and "size" (study size).

References

Galbraith RF (1988a), Graphical display of estimates having differing standard errors. Technometrics, 30, 271--281.

Galbraith RF (1988b), A note on graphical presentation of estimated odds ratios from several clinical trials. Statistics in Medicine, 7, 889--894. Light RJ & Pillemer DB (1984), Summing Up. The Science of Reviewing Research. Cambridge: Havard University Press.

Sterne JAC & Egger M (2001), Funnel plots for detecting bias in meta-analysis: Guidelines on choice of axis. Journal of Clinical Epidemiology, 54, 1046--1055.

See Also

metabias, metabin, metagen

Examples

data(Olkin95)
meta1 <- metabin(event.e, n.e, event.c, n.c,
                 data=Olkin95, subset=c(41,47,51,59),
                 sm="RR", meth="I")

##
## Same results:
##
oldpar <- par(mfrow=c(2,2))
funnel(meta1)
funnel(meta1$TE, meta1$seTE, sm="RR")
par(oldpar)


oldpar <- par(mfrow=c(2,2))
funnel(meta1)
funnel(meta1, yaxis="inv")
funnel(meta1, yaxis="size")
par(oldpar)


funnel(meta1, comb.f=TRUE, xlim=c(0.1, 10), axes=FALSE)
box()
axis(1, at=c(0.1, 0.5, 1, 2, 10))
axis(2)

radial(meta1, level=0.95)