sig.score: Function to compute signature scores as linear combination of...

In bhklab/genefu: Computation of Gene Expression-Based Signatures in Breast Cancer

Function to compute signature scores as linear combination of gene expressions

Description

This function computes a signature score from a gene list (aka gene signature), i.e. a signed average as published in Sotiriou et al. 2006 and Haibe-Kains et al. 2009.

Usage

sig.score(x, data, annot, do.mapping = FALSE, mapping, size = 0,
  cutoff = NA, signed = TRUE, verbose = FALSE)

Arguments

x	Matrix containing the gene(s) in the gene list in rows and at least three columns: "probe", "EntrezGene.ID" and "coefficient" standing for the name of the probe, the NCBI Entrez Gene id and the coefficient giving the direction and the strength of the association of each gene in the gene list.
data	Matrix of gene expressions with samples in rows and probes in columns, dimnames being properly defined.
annot	Matrix of annotations with at least one column named "EntrezGene.ID", dimnames being properly defined.
do.mapping	TRUE if the mapping through Entrez Gene ids must be performed (in case of ambiguities, the most variant probe is kept for each gene), FALSE otherwise.
mapping	Matrix with columns "EntrezGene.ID" and "probe" used to force the mapping such that the probes are not selected based on their variance.
size	Integer specifying the number of probes to be considered in signature computation. The probes will be sorted by absolute value of coefficients.
cutoff	Only the probes with coefficient greater than cutoff will be considered in signature computation.
signed	TRUE if only the sign of the coefficient must be considered in signature computation, FALSE otherwise.
verbose	TRUE to print informative messages, FALSE otherwise.

Value

A list with items:

• score: Signature score.

• mapping: Mapping used if necessary.

• probe: If mapping is performed, this matrix contains the correspondence between the gene list (aka signature) and gene expression data.

References

Sotiriou C, Wirapati P, Loi S, Harris A, Bergh J, Smeds J, Farmer P, Praz V, Haibe-Kains B, Lallemand F, Buyse M, Piccart MJ and Delorenzi M (2006) "Gene expression profiling in breast cancer: Understanding the molecular basis of histologic grade to improve prognosis", Journal of National Cancer Institute, 98:262-272 Haibe-Kains B (2009) "Identification and Assessment of Gene Signatures in Human Breast Cancer", PhD thesis at Universite Libre de Bruxelles, http://theses.ulb.ac.be/ETD-db/collection/available/ULBetd-02182009-083101/

Examples

# load NKI data
data(nkis)
# load GGI signature
data(sig.ggi)
# make of ggi signature a gene list
ggi.gl <- cbind(sig.ggi[ ,c("probe", "EntrezGene.ID")],
  "coefficient"=ifelse(sig.ggi[ ,"grade"] == 1, -1, 1))
# computation of signature scores
ggi.score <- sig.score(x=ggi.gl, data=data.nkis, annot=annot.nkis,
  do.mapping=TRUE, signed=TRUE, verbose=TRUE)
str(ggi.score)

bhklab/genefu documentation built on Nov. 30, 2024, 9:03 p.m.