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aroma.affymetrix (version 2.2.0)

LimmaBackgroundCorrection: The LimmaBackgroundCorrection class

Description

Package: aroma.affymetrix Class LimmaBackgroundCorrection Object ~~| ~~+--AromaTransform ~~~~~~~| ~~~~~~~+--Transform ~~~~~~~~~~~~| ~~~~~~~~~~~~+--ProbeLevelTransform ~~~~~~~~~~~~~~~~~| ~~~~~~~~~~~~~~~~~+--BackgroundCorrection ~~~~~~~~~~~~~~~~~~~~~~| ~~~~~~~~~~~~~~~~~~~~~~+--LimmaBackgroundCorrection Directly known subclasses: NormExpBackgroundCorrection public static class LimmaBackgroundCorrection extends BackgroundCorrection This class represents the various "background" correction methods implemented in the limma package.

Usage

LimmaBackgroundCorrection(..., args=NULL, addJitter=FALSE, jitterSd=0.2)

Arguments

...
Arguments passed to the constructor of BackgroundCorrection.
args
A list of additional arguments passed to the correction algorithm.
addJitter
If TRUE, Zero-mean gaussian noise is added to the signals before being background corrected.
jitterSd
Standard deviation of the jitter noise added.

Fields and Methods

Methods: rll{ process Performs background correction. } Methods inherited from BackgroundCorrection: process Methods inherited from Transform: getOutputDataSet, getOutputDataSetOLD20090509, getOutputFiles Methods inherited from AromaTransform: getExpectedOutputFiles, getExpectedOutputFullnames, getFullName, getInputDataSet, getName, getOutputDataSet, getOutputDataSet0, getOutputFiles, getPath, getTags, isDone, process, setTags Methods inherited from Object: asThis, getChecksum, $, $<-, [[, [[<-, as.character, attach, attachLocally, clearCache, clearLookupCache, clone, detach, equals, extend, finalize, gc, getEnvironment, getFieldModifier, getFieldModifiers, getFields, getInstantiationTime, getStaticInstance, hasField, hashCode, ll, load, objectSize, print, registerFinalizer, save

Jitter noise

The fitting algorithm of the normal+exponentital background correction model may not converge if there too many small and discrete signals. To overcome this problem, a small amount of noise may be added to the signals before fitting the model. This is an ad hoc solution that seems to work. However, adding Gaussian noise may generate non-positive signals.

Details

By default, only PM signals are background corrected and MMs are left unchanged.

See Also

Internally, backgroundCorrect is used.