% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/bubble.R
\name{bubble.metareg}
\alias{bubble.metareg}
\alias{bubble}
\title{Bubble plot to display the result of a meta-regression}
\usage{
\method{bubble}{metareg}(
  x,
  xlim,
  ylim,
  xlab,
  ylab,
  cex,
  min.cex = 0.5,
  max.cex = 5,
  pch = 21,
  col = "black",
  bg = "darkgray",
  lty = 1,
  lwd = 1,
  col.line = "black",
  studlab = FALSE,
  cex.studlab = 0.8,
  pos.studlab = 2,
  offset = 0.5,
  regline = TRUE,
  backtransf = x$.meta$x$backtransf,
  ref,
  col.ref = "lightgray",
  lty.ref = 1,
  lwd.ref = 1,
  pscale = x$.meta$x$pscale,
  irscale = x$.meta$x$irscale,
  axes = TRUE,
  box = TRUE,
  ...
)

bubble(x, ...)
}
\arguments{
\item{x}{An object of class \code{metareg}.}

\item{xlim}{The x limits (min,max) of the plot.}

\item{ylim}{The y limits (min,max) of the plot.}

\item{xlab}{A label for the x-axis.}

\item{ylab}{A label for the y-axis.}

\item{cex}{The magnification to be used for plotting symbols.}

\item{min.cex}{Minimal magnification for plotting symbols.}

\item{max.cex}{Maximal magnification for plotting symbols.}

\item{pch}{The plotting symbol(s) used for individual studies.}

\item{col}{A vector with colour of plotting symbols.}

\item{bg}{A vector with background colour of plotting symbols (only
used if \code{pch} in \code{21:25}).}

\item{lty}{The line type for the meta-regression line.}

\item{lwd}{The line width for the meta-regression line.}

\item{col.line}{Colour for the meta-regression line.}

\item{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 the numer of studies in the
meta-analysis then).}

\item{cex.studlab}{The magnification for study labels.}

\item{pos.studlab}{Position of study labels, see argument
\code{pos} in \code{\link{text}}.}

\item{offset}{Offset for study labels (see \code{\link{text}}).}

\item{regline}{A logical indicating whether a regression line
should be added to the bubble plot.}

\item{backtransf}{A logical indicating whether results for relative
summary measures (argument \code{sm} equal to \code{"OR"},
\code{"RR"}, \code{"HR"}, or \code{"IRR"}) should be back
transformed. If \code{backtransf=TRUE}, results for
\code{sm="OR"} are printed as odds ratios rather than log odds
ratios, for example.}

\item{ref}{A numerical giving the reference value to be plotted as
a line in the bubble plot. No reference line is plotted if
argument \code{ref} is equal to \code{NA}.}

\item{col.ref}{Colour of the reference line.}

\item{lty.ref}{The line type for the reference line.}

\item{lwd.ref}{The line width for the reference line.}

\item{pscale}{A numeric giving scaling factor for printing of
probabilities.}

\item{irscale}{A numeric defining a scaling factor for printing of
incidence rates.}

\item{axes}{Either a logical or a character string equal to \code{"x"},
\code{"y"} or \code{"xy"} indicating whether x- and y-axis should be
printed.}

\item{box}{A logical indicating whether a box should be printed.}

\item{\dots}{Graphical arguments as in \code{par} may also be
passed as arguments.}
}
\description{
Draw a bubble plot to display the result of a meta-regression.
}
\details{
A bubble plot can be used to display the result of a
meta-regression. It is a scatter plot with the treatment effect for
each study on the y-axis and the covariate used in the
meta-regression on the x-axis. Typically, the size of the plotting
symbol is inversely proportional to the variance of the estimated
treatment effect (Thompson & Higgins, 2002).

Argument \code{cex} specifies the plotting size for each individual
study. If this argument is missing the weights from the
meta-regression model will be used (which typically is a random
effects model). Use \code{cex="common"} in order to utilise weights
from a common effect model to define the size of the plotted
symbols (even for a random effects meta-regression). If a vector
with individual study weights is provided, the length of this
vector must be of the same length as the number of studies.

Arguments \code{min.cex} and \code{max.cex} can be used to define
the size of the smallest and largest plotting symbol. The plotting
size of the most precise study is set to \code{max.cex} whereas the
plotting size of all studies with a plotting size smaller than
\code{min.cex} will be set to \code{min.cex}.

For a meta-regression with more than one covariate. Only a scatter plot of
the first covariate in the regression model is shown. In this case the
effect of the first covariate adjusted for other covariates in the
meta-regression model is shown.

For a factor or categorial covariate separate bubble plots for each
group compared to the baseline group are plotted.
}
\examples{
data(Fleiss1993cont)

# Add some (fictitious) grouping variables:
Fleiss1993cont$age <- c(55, 65, 52, 65, 58)
Fleiss1993cont$region <- c("Europe", "Europe", "Asia", "Asia", "Europe")

m1 <- metacont(n.psyc, mean.psyc, sd.psyc, n.cont, mean.cont, sd.cont,
  data = Fleiss1993cont, sm = "SMD")

mr1 <- metareg(m1, region)
mr1

bubble(mr1)
bubble(mr1, lwd = 2, col.line = "blue")

mr2 <- metareg(m1, age)
mr2

bubble(mr2, lwd = 2, col.line = "blue", xlim = c(50, 70))
bubble(mr2, lwd = 2, col.line = "blue", xlim = c(50, 70), cex = "common")

# Do not print regression line
#
bubble(mr2, lwd = 2, col.line = "blue", xlim = c(50, 70), regline = FALSE)

}
\references{
Thompson SG, Higgins JP (2002):
How should meta-regression analyses be undertaken and interpreted?
\emph{Statistics in Medicine},
\bold{21}, 1559--73
}
\seealso{
\code{\link{metagen}}, \code{\link{metainf}}
}
\author{
Guido Schwarzer \email{guido.schwarzer@uniklinik-freiburg.de}
}
\keyword{hplot}
