\HeaderA{plotDensities}{Individual-channel Densities Plot}{plotDensities}
\keyword{hplot}{plotDensities}
\begin{Description}\relax
Plots the densities of individual-channel intensities for two-color microarray data.
\end{Description}
\begin{Usage}
\begin{verbatim}
plotDensities(object, log=TRUE, arrays=NULL, singlechannels=NULL, groups=NULL, col=NULL) 
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{object}] an \code{RGList} or \code{MAList} object. \code{RGList} objects containing logged or unlogged intensities can be accommodated using the \code{log.transform} argument.
\item[\code{log}] logical, should densities be formed and plotted for the log-intensities (\code{TRUE}) or raw intensities (\code{FALSE})?
\item[\code{arrays}] vector of integers giving the arrays from which the
individual-channels will be selected to be plotted.
Corresponds to columns of \code{M}
and \code{A} (or \code{R} and \code{G}).  Defaults to all arrays.
\item[\code{singlechannels}] vector of integers indicating which
individual-channels will be selected to be plotted.  Values correspond
to the columns of the matrix of \code{cbind(R,G)} and range
between \code{1:ncol(R)} for red channels and
\code{( (ncol(R)+1):(ncol(R)+ncol(G)) )} for the green
channels in \code{object}.
Defaults to all channels.
\item[\code{groups}] vector of consecutive integers beginning at 1 indicating
the groups of arrays or individual-channels (depending on which of
\code{arrays} or \code{singlechannels} are non \code{NULL}).  This is used
to color any groups of the individual-channel densities.
If \code{NULL} (default), \code{groups} correspond to the
red and green channels.  If both \code{arrays} and
\code{singlechannels} are \code{NULL} all arrays are selected and
groups (if specified) must correspond to the arrays.
\item[\code{col}] vector of colors of the same length as the number of
different groups. If \code{NULL} (default) the \code{col} equals
\code{c("red","green")}.  See details for more specifications.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
This function is used as a data display technique associated with between-array normalization, especially individual-channel normalization methods such as quantile-normalization.
See the section on between-array normalization in the LIMMA User's Guide.

If no \code{col} is specified, the default is to color individual channels
according to red and green. If both \code{arrays} and \code{groups} are
non-\code{NULL}, then the length of \code{groups} must equal the length
of \code{arrays} and the maximum of \code{groups} (i.e. the number of
groups) must equal the length of \code{col} otherwise the default color
of black will be used for all individual-channels.
If \code{arrays} is \code{NULL} and both \code{singlechannels} and
\code{groups} are non-\code{NULL}, then the length of \code{groups} must
equal the length of \code{singlechannels} and the maximum of \code{groups}
(i.e. the number of groups) must equal the length of \code{col}
otherwise the default color of black will be used for all individual-channels.
\end{Details}
\begin{Value}
A plot is created on the current graphics device.
\end{Value}
\begin{Author}\relax
Natalie Thorne
\end{Author}
\begin{SeeAlso}\relax
An overview of diagnostic plots in LIMMA is given in \LinkA{09.Diagnostics}{09.Diagnostics}.
There is a section using \code{plotDensities} in conjunction with between-array normalization
in the \emph{\LinkA{LIMMA User's Guide}{LIMMA User's Guide}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
library(sma)
data(MouseArray)

#  no normalization but background correction is done
MA.n <- MA.RG(mouse.data)

#  Default settings for plotDensities.
plotDensities(MA.n)

#  One can reproduce the default settings.
plotDensities(MA.n,arrays=c(1:6),groups=c(rep(1,6),rep(2,6)),
col=c("red","green"))

#  Color R and G individual-channels by blue and purple.
plotDensities(MA.n,arrays=NULL,groups=NULL,col=c("blue","purple"))

#  Indexing individual-channels using singlechannels (arrays=NULL).
plotDensities(MA.n,singlechannels=c(1,2,7))

#  Change the default colors from c("red","green") to c("pink","purple")
plotDensities(MA.n,singlechannels=c(1,2,7),col=c("pink","purple"))

#  Specified too many colors since groups=NULL defaults to two groups.
plotDensities(MA.n,singlechannels=c(1,2,7),col=c("pink","purple","blue"))

#  Three individual-channels, three groups, three colors.
plotDensities(MA.n,singlechannels=c(1,2,7),groups=c(1,2,3),
col=c("pink","purple","blue"))

#  Three individual-channels, one group, one color.
plotDensities(MA.n,singlechannels=c(1,2,7),groups=c(1,1,1),
col=c("purple"))

#  All individual-channels, three groups (ctl,tmt,reference), three colors.
plotDensities(MA.n,singlechannels=c(1:12),
groups=c(rep(1,3),rep(2,3),rep(3,6)),col=c("darkred","red","green"))

\end{ExampleCode}
\end{Examples}