baujat.meta: Baujat plot to explore heterogeneity in meta-analysis

In meta: General Package for Meta-Analysis

Baujat plot to explore heterogeneity in meta-analysis

Description

Draw a Baujat plot to explore heterogeneity in meta-analysis.

Usage

## S3 method for class 'meta'
baujat(
  x,
  yscale = 1,
  xlim,
  ylim,
  xlab = "Contribution to overall heterogeneity",
  ylab = "Influence on overall result",
  pch = 21,
  cex = 1,
  col = "black",
  bg = "darkgray",
  studlab = TRUE,
  cex.studlab = 0.8,
  pos.studlab,
  offset = 0.5,
  xmin = 0,
  ymin = 0,
  grid = TRUE,
  col.grid = "lightgray",
  lty.grid = "dotted",
  lwd.grid = par("lwd"),
  pty = "s",
  pooled,
  ...
)

Arguments

x	An object of class meta.
yscale	Scaling factor for values on y-axis.
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.
pch	The plotting symbol used for individual studies.
cex	The magnification to be used for plotting symbol.
col	A vector with colour of plotting symbols.
bg	A vector with background colour of plotting symbols (only used if pch in 21:25).
studlab	A logical indicating whether study labels should be printed in the graph. A vector with study labels can also be provided (must be of same length as x$TE then).
cex.studlab	The magnification for study labels.
pos.studlab	Position of study labels, see argument pos in text.
offset	Offset for study labels (see text).
xmin	A numeric specifying minimal value to print study labels (on x-axis).
ymin	A numeric specifying minimal value to print study labels (on y-axis).
grid	A logical indicating whether a grid is printed in the plot.
col.grid	Colour for grid lines.
lty.grid	The line type for grid lines.
lwd.grid	The line width for grid lines.
pty	A character specifying type of plot region (see par).
pooled	A character string indicating whether a common effect or random effects model is used for pooling. Either missing (see Details), "common" or "random", can be abbreviated.
...	Graphical arguments as in par may also be passed as arguments.

Details

Baujat et al. (2002) introduced a scatter plot to explore heterogeneity in meta-analysis. On the x-axis the contribution of each study to the overall heterogeneity statistic (see list object Q of the meta-analysis object x) is plotted. On the y-axis the standardised difference of the overall treatment effect with and without each study is plotted; this quantity describes the influence of each study on the overal treatment effect.

Information from object x is utilised if argument pooled is missing. A common effect model is assumed (pooled="common") if argument x$common is TRUE; a random effects model is assumed (pooled="random") if argument x$random is TRUE and x$common is FALSE.

Internally, the metainf function is used to calculate the values on the y-axis.

Value

A data.frame with the following variables:

x	Coordinate on x-axis (contribution to heterogeneity statistic)
y	Coordinate on y-axis (influence on overall treatment effect)

Author(s)

Guido Schwarzer [e-mail]

References

Baujat B, Mahé C, Pignon JP, Hill C (2002): A graphical method for exploring heterogeneity in meta-analyses: Application to a meta-analysis of 65 trials. Statistics in Medicine, 30, 2641–52

See Also

metagen, metainf

Examples

data(Olkin1995)

# Only consider first ten studies
m1 <- metabin(ev.exp, n.exp, ev.cont, n.cont,
  data = Olkin1995, sm = "OR", method = "I", studlab = paste(author, year),
  subset = 1:10)

# Generate Baujat plot
baujat(m1)

## Not run: 
m1 <- metabin(ev.exp, n.exp, ev.cont, n.cont,
  data = Olkin1995, sm = "OR", method = "I", studlab = paste(author, year))

# Do not print study labels if the x-value is smaller than 4 and
# the y-value is smaller than 1
baujat(m1, yscale = 10, xmin = 4, ymin = 1)

# Change position of study labels
baujat(m1, yscale = 10, xmin = 4, ymin = 1,
       pos = 1, xlim = c(0, 6.5))

# Generate Baujat plot and assign x- and y- coordinates to R object
# b1
b1 <- baujat(m1)

# Calculate overall heterogeneity statistic
sum(b1$x)
m1$Q

## End(Not run)

meta documentation built on Oct. 31, 2024, 5:07 p.m.