PGSEA {PGSEA} | R Documentation |
This package contains functions for parametric analysis of gene expression data. This type of analysis can assist in determining of lists of genes, such as those deregulated in defined experimental systems, are similarly disregulated in other data sets.
This function subsets the data based on lists of genes, computes a summary statistic for each gene list, and returns the results in a convenient form.
PGSEA(exprs, cl, range = c(25, 500), ref = NULL, center = TRUE, p.value = 0.005, weighted = TRUE, ...)
exprs |
matrix expression data, a numeric matrix, eSet, or exprSet |
cl |
gene set list - "GeneSetCollection" or list of "SMC" objects |
range |
a 2 element vector describing the min and max length of concepts to analyze |
ref |
a vector containing the index of reference samples from which to make comparisons. Defaults to NULL (internally referenced samples) |
center |
boolean - median center gene expression matrix columns prior to analysis. Can be helpful if 'ref' is used |
p.value |
numeric p.value threshold or NA to return all data or TRUE to return a matrix of p.values |
weighted |
boolean - weight results by the size of each gene list |
... |
extra arguments passed along to FUN |
Gene expression values are separated into subsets based on the lists
of genes contained in the cl argument. This can be a "GeneSetCollection" or a list of "SMC" (Simple Molecular Concept) objects.
For example, readGmt
can be used to produce a 'smc'
object list from a simple tab-delimited text file. The gene
expression values from each of these gene lists is extracted and a
summary statistic is computed for each subset (or region in the case of chromsomal bands/arms).
The expression data must have the same identifiers as the list of
genes being tested. If they are not, the expression data can be
converted using the aggregateExprs
function, that can use a
current annotation environment to convert and condense the gene
expression data.
By default the method set out by Kim and Volsky http://www.biomedcentral.com/1471-2105/6/144 is applied to the gene set. If weighted==FALSE than the default t.test
fuction is used.
The function is set up to perform the analysis on individual
samples. For convenient method to analyze groups of samples, see the
"Limma User's Guide" for more information on how to see up a contrast
matrix and perform a linear model fit. The coefficents of the fit
can then be used a input into the PGSEA
function.
If p.value is set to a number, a matrix of results that pass at that significance is returned, of size <number of samples> x <number of molecular concepts>.
If p.value is set to NA, all results are returned.
If p.value is set to TRUE, then a list is returned that consists of the PGSEA results as well as their p.values.
http://www.biomedcentral.com/1471-2105/6/144
Kim SY, Volsky DJ., kyle.furge@vai.org and karl.dykema@vai.org
PGSEA: Parametric Analysis of Gene Set Enrichment
datadir <- system.file("data", package = "PGSEA") sample <- readGmt(file.path(datadir, "sample.gmt")) data(nbEset) pg <- PGSEA(nbEset,cl=sample,ref=1:5) print(pg[,-c(1:5)])