a4 (version 1.20.0)

filterVarInt: Filter Features On Intensity and Variance

Description

Function to filter on intensity and variance as typically used in gene expression studies

Usage

filterVarInt(object, IntCutOff = log2(100), IntPropSamples = 0.25, VarCutOff = 0.5)

Arguments

object

ExpressionSet object

IntCutOff

cut-off value used for the intensity filter

IntPropSamples

proportion of samples used by the intensity filter; by default IntPropSamples si set to 0.25 is

VarCutOff

cut-off value used for the variance filter

Value

• Object of class ExpressionSet containing only the features that pass the variance and intensity filter.

Details

The intensity filter implies that (by default) the intensity levels must be greater than log2(100) in at least 25 percent of the samples. The variance filter requires that the features have an interquartile range (IQR) greater than 0.5. Note that the IQR is quite insensitive to outliers such that genes with outlying expression values in a few samples are excluded as long as their overall variation is small.

References

Gentleman, R. et al. (2005). Bioinformatics and Computational Biology Solutions using R and BioConductor, New York: Springer. Goehlmann, H. and W. Talloen (2009). Gene Expression Studies Using Affymetrix Microarrays, Chapman & Hall/CRC, p. 128.

See Also

pOverA, filterfun

Examples

if (require(ALL)){
  data(ALL, package = "ALL")
  fALL <- filterVarInt(ALL)
  fALL
}