TestGeneSets: Test a List of Gene Sets Using a Specific Statistical Method

Description Usage Arguments Details Value Author(s) References See Also Examples

View source: R/TestGeneSets.R

Description

A wrapper function that invokes a specific statistical method from the ones available in package GSAR (see Rahmatallah et. al. 2014, Rahmatallah et. al. 2012 and Friedman and Rafsky 1979 for details) to test a list of gene sets in a sequential order and returns results in a list object.

Usage

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TestGeneSets(object, group, geneSets=NULL, min.size=10, max.size=500, 
test=NULL, nperm=1000, mst.order=1, pvalue.only=TRUE)

Arguments

object

a numeric matrix with columns and rows respectively corresponding to samples and features.

group

a numeric vector indicating group associations for samples. Possible values are 1 and 2.

geneSets

a list of character vectors providing the identifiers of features to be considered in each gene set.

min.size

a numeric value indicating the minimum allowed gene set size. Default value is 10.

max.size

a numeric value indicating the maximum allowed gene set size. Default value is 500.

test

a character parameter indicating which statistical method to use for testing the gene sets. Must be one of “GSNCAtest”, “WWtest”, “KStest”, “MDtest”, “RKStest”, “RMDtest”.

nperm

number of permutations used to estimate the null distribution of the test statistic. If not given, a default value 1000 is used.

mst.order

numeric value to indicate the consideration of the union of the first mst.order MSTs when “RKStest” or “RMDtest” are used. Default value is 1. Maximum allowed value is 5.

pvalue.only

logical. If TRUE (default), the p-value is returned. If FALSE a list of length three containing the observed statistic, the vector of permuted statistics, and the p-value is returned.

Details

This is a wrapper function that facilitates the use of any statistical method in package GSAR for multiple gene sets that are provided in a list object. The function filters out any gene that is abscent in the considered data (input parameter object) from the gene sets and discard any set that is too small in size (has less than min.size genes) or too large (has more than max.size genes). The function performs the specified method for all the remaining gene sets in a sequential order and return results in a list object.

Value

A list object of length equals the length of the provided gene set list. When pvalue.only=TRUE (default), each item in the returned list by function TestGeneSets consists of a numeric p-value indicating the attained significance level obtained by the specified method. When pvalue.only=FALSE, each item in the returned list is a list of length 3 with the following components:

statistic

the value of the observed test statistic.

perm.stat

numeric vector of the resulting test statistic for nperm random permutations of sample labels.

p.value

p-value indicating the attained significance level.

Author(s)

Yasir Rahmatallah and Galina Glazko

References

Rahmatallah Y., Emmert-Streib F. and Glazko G. (2014) Gene sets net correlations analysis (GSNCA): a multivariate differential coexpression test for gene sets. Bioinformatics 30, 360–368.

Rahmatallah Y., Emmert-Streib F. and Glazko G. (2012) Gene set analysis for self-contained tests: complex null and specific alternative hypotheses. Bioinformatics 28, 3073–3080.

Friedman J. and Rafsky L. (1979) Multivariate generalization of the Wald-Wolfowitz and Smirnov two-sample tests. Ann. Stat. 7, 697–717.

See Also

GSNCAtest, WWtest, MDtest, KStest, RKStest, RMDtest.

Examples

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## generate a feature set of size 50 in two conditions
## where each condition has 20 samples
## use multivariate normal distribution
library(MASS)
ngenes <- 50
nsamples <- 40
## let the mean vector have zeros of length 50 for both conditions
zero_vector <- array(0,c(1,ngenes))

## set the covariance matrix to be an identity matrix for both conditions
cov_mtrx <- diag(ngenes)
gp <- mvrnorm(nsamples, zero_vector, cov_mtrx)
## apply a mean shift of 5 to the first 10 features under condition 1
gp[1:20,1:10] <- gp[1:20,1:10] + 5
dataset <- aperm(gp, c(2,1))
## assign a unique identifier to each gene
rownames(dataset) <- as.character(c(1:ngenes))
## first 20 samples belong to condition 1
## second 20 samples belong to condition 2
sample.labels <- c(rep(1,20),rep(2,20))
## construct 3 named gene sets such that they respectively consist of 
## genes 1 to 20, 11 to 40, and 31 to 50. Notice that gene sets 
## can have intersections and can be of different sizes 
## Sine only the first 10 genes have a significant difference between 
## the two conditions the only the first gene set (set1) returns a 
## small p-value when KStest is selected
geneSets <- list("set1"=as.character(c(1:20)), "set2"=as.character(c(11:40)), 
"set3"=as.character(c(31:40)))
results <- TestGeneSets(object=dataset, group=sample.labels, 
geneSets=geneSets, test="KStest")

GSAR documentation built on Nov. 1, 2018, 2:26 a.m.