MAMA (version 2.1.0)

zScores: Function for Meta-analysis of gene expression data

Description

Functions for computing zScores for FEM and REM and computing FDR. This are modification of functions found in GeneMeta package.

Usage

zScores(esets, classes, useREM=TRUE, CombineExp=1:length(esets))
zScorePermuted(esets, classes, useREM=TRUE, CombineExp=1:length(esets))
zScoreFDR(esets, classes, useREM=TRUE, nperm=1000, CombineExp=1:length(esets))
multExpFDR(theScores, thePermScores, type="pos")

Arguments

esets

A list of matrices, one expression set per experiment. All experiments must have the same variables(genes).

classes

A list of class memberships, one per experiment. Each list can only contain 2 levels.

useREM

A logical value indicating whether or not to use a REM, TRUE, or a FEM, FALSE, for combining the z scores.

theScores

A vector of scores (e.g. t-statistics or z scores)

thePermScores

A vector of permuted scores (e.g. t-statistics or z scores)

type

"pos", "neg" or "two.sided"

nperm

number of permutations to calculate the FDR

CombineExp

A vector of integer- which experiments should be combined-default:all experiments

Value

• A matrix with one row for each probe(set) and the following columns:
• zSco_Ex_
  For each single experiment the standardized mean difference, Effect_Ex_, divided by the estimated standard deviation, the square root of the EffectVar_Ex_ column.
• MUvals
  The combined standardized mean difference (using a FEM or REM)
• MUsds
  The standard deviation of the MUvals.
• zSco
  The z statistic - the MUvals divided by their standard deviations, MUsds.
• Qvals
  Cochran's Q statistic for each gene.
• df
  The degree of freedom for the Chi-square distribution. This is equal to the number of combined experiments minus one.
• Qpvalues
  The probability that a Chi-square random variable, with df degrees of freedom) has a higher value than the value from the Q statistic.
• Chisq
  The probability that a Chi-square random variate (with 1 degree of freedom) has a higher value than the value of zSco^2.
• Effect_Ex_
  The standardized mean difference for each single experiment.
• EffectVar_Ex_
  The variance of the standardized mean difference for each single experiment.

Details

The function zScores implements the approach of Choi et al. for MetaArray. The function zScorePermuted applies zScore to a single permutation of the class labels. The function zScoreFDR computes a FDR for each gene, both for each single experiment and for the combined experiment. The FDR is calculated as described in Choi et al. Up to now ties in the zscores are not taken into account in the calculation. The function might produce incorrect results in that case. The function also computes zScores, both for the combines experiment and for each single experiment.

References

Choi et al, Combining multiple microarray studies and modeling interstudy variation. Bioinformatics, 2003, i84-i90.

Examples

data(ColonData)
esets <- GEDM(ColonData)
classes <- selectClass(ColonData, "satelite", "binary")
theScores <- zScores(esets, classes, useREM = FALSE)