Funnel plot to examine publication bias

Description

Function to examine publication bias. For both fixed- and random-effects models, estimates from no-pooling effects model are used as study-specific estimates. For random-effects models, the corresponding fixed-effects models are implemented at background to obtain pooled estimate. For example, if users call bmeta to run random-effects meta-analysis with normal prior, fixed-effects meta-analysis with normal prior are implemented at background to obtain pooled estimate for graphing. In the absence of publication and heterogeneity, the scatter resembles a symmetrical funnel and the triangle area formed by connecting the centred summary estimate with its 2.5% and 97.5% quantiles on either side includes about 95% of the studies if the fixed-effects model assumption holds (i.e. all the studies estimate the same effect).

Usage

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Arguments

x

a bmeta object with results of the model

xlab

title of x-axis. If unspecified, the function sets an appropriate lable by default.

ylab

title of x-axis. If unspecified, the function sets an appropriate lable by default.

title

title of the plot if specified

xlim

horozontal limits of the plot region. If unspecified, the function sets the horizontal plot limits to (-6,6).

Author(s)

Tao Ding Gianluca Baio

Examples

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### Read and format the data (binary)
data = read.csv(url("http://www.statistica.it/gianluca/bmeta/Data-bin.csv"))

### List data for binary outcome 
data.list <- list(y0=data$y0,y1=data$y1,n0=data$n0,n1=data$n1) 

### Select random-effects meta-analysis with t-distribution prior for binary
### data
x <- bmeta(data.list, outcome="bin", model="std.dt", type="ran")

### using output from bmeta to produce funnel plot 
funnel.plot(x)

### using output from bmeta and specify title of the plot 
funnel.plot(x,title="funnel plot")

### using output from bmeta and specify the limit of x-axis and title
funnel.plot(x,title="funnel plot",xlim=c(-2,1))