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\name{camera}
\alias{camera.DGEList}
\alias{camera.DGEGLM}
\alias{cameraPR.DGELRT}
\title{Competitive Gene Set Tests for Digital Gene Expression Data}
\description{
Test whether a set of genes is highly ranked relative to other genes in terms of differential expression, accounting for inter-gene correlation.
}
\usage{
\method{camera}{DGEList}(y, index, design = NULL, contrast = ncol(design), weights = NULL,
use.ranks = FALSE, allow.neg.cor=FALSE, inter.gene.cor=0.01, sort = TRUE, \dots)
\method{camera}{DGEGLM}(y, index, design = NULL, contrast = ncol(design), weights = NULL,
use.ranks = FALSE, allow.neg.cor=FALSE, inter.gene.cor=0.01, sort = TRUE, \dots)
\method{cameraPR}{DGELRT}(statistic, index, use.ranks = FALSE, inter.gene.cor=0.01, sort = TRUE, \dots)
}
\arguments{
\item{y}{a \code{DGEList} object containing dispersion estimates or a \code{DGEGLM} object.}
\item{index}{an index vector or a list of index vectors. Can be any vector such that \code{y[index,]} selects the rows corresponding to the test set. The list can be made using \code{\link{ids2indices}}.}
\item{design}{design matrix. Defaults to \code{y$design} or, if that is NULL, to \code{model.matrix(~y$samples$group)}.}
\item{contrast}{contrast of the linear model coefficients for which the test is required. Can be an integer specifying a column of \code{design}, or else a numeric vector of same length as the number of columns of \code{design}.}
\item{weights}{numeric matrix of observation weights of same size as \code{y}, or a numeric vector of array weights with length equal to \code{ncol(y)}, or a numeric vector of gene weights with length equal to \code{nrow(y)}.}
\item{use.ranks}{do a rank-based test (\code{TRUE}) or a parametric test (\code{FALSE})?}
\item{allow.neg.cor}{should reduced variance inflation factors be allowed for negative correlations?}
\item{inter.gene.cor}{numeric, optional preset value for the inter-gene correlation within tested sets. If \code{NA} or \code{NULL}, then an inter-gene correlation will be estimated for each tested set.}
\item{sort}{logical, should the results be sorted by p-value?}
\item{statistic}{a \code{DGELRT} object.}
\item{\dots}{other arguments are not currently used}
}
\details{
Camera is a competitive gene set test proposed by Wu and Smyth (2012) for microarray data and \code{camera} and implemented as an S3 generic function in the limma package.
It is often used for gene set enrichment analyses (GSEA) together with a database of gene sets such as the MSigDB.
Here we provide \code{camera} methods for DGEList and DGEGLM class objects.
The negative binomial count data is converted to approximate normal deviates by computing mid-p quantile residuals (Dunn and Smyth, 1996; Routledge, 1994), under the null hypothesis that the contrast is zero, and the normal deviates are then passed to limma's camera function.
The \code{cameraPR} function is a variation of the camera method for pre-ranked diffential expression statistics.
We provide here a \code{cameraPR} method for DGELRT objects.
}
\value{
A data.frame giving the gene set results, with a row for each gene set defined by \code{index}.
If \code{sort=TRUE} then results are sorted in decreasing order of significance.
See \code{\link{camera}} for details.
}
\author{Yunshun Chen, Gordon Smyth}
\references{
Dunn PK, Smyth GK (1996).
Randomized quantile residuals.
\emph{Journal of Computational and Graphical Statistics} 5, 236-244.
\doi{10.1080/10618600.1996.10474708}
\url{https://gksmyth.github.io/pubs/residual.html}
Routledge RD (1994).
Practicing safe statistics with the mid-p.
\emph{Canadian Journal of Statistics} 22, 103-110.
Wu D, Smyth GK (2012). Camera: a competitive gene set test accounting for inter-gene correlation.
\emph{Nucleic Acids Research} 40, e133.
\doi{10.1093/nar/gks461}
}
\seealso{
\code{\link{camera}}.
}
\examples{
mu <- matrix(10, 100, 4)
group <- factor(c(0,0,1,1))
design <- model.matrix(~group)
# First set of 10 genes that are genuinely differentially expressed
iset1 <- 1:10
mu[iset1,3:4] <- mu[iset1,3:4]+10
# Second set of 10 genes are not DE
iset2 <- 11:20
# Generate counts and create a DGEList object
y <- matrix(rnbinom(100*4, mu=mu, size=10),100,4)
y <- DGEList(counts=y, group=group)
# Estimate dispersions
y <- estimateDisp(y, design)
# Gene set tests
camera(y, iset1, design)
camera(y, iset2, design)
camera(y, list(set1=iset1,set2=iset2), design)
# Alternative pre-ranked version
fit <- glmQLFit(y, design)
q <- glmQLFTest(fit)
cameraPR(q, list(set1=iset1,set2=iset2))
}
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