retentionTimeCorrection-peakPantheRAnnotation-method: Apply retention time correction methods to adjust the...

In peakPantheR: Peak Picking and Annotation of High Resolution Experiments

Description

Performs retention time correction to re-adjust the expected retention time position of compounds. Requires an annotated peakPantheRAnnotation object (isAnnotated=TRUE). The original rt value is used as expected and the observed deviation measured in the rt_dev_sec field is taken as the deviation to be corrected.

Usage

## S4 method for signature 'peakPantheRAnnotation'
retentionTimeCorrection(
    annotationObject,
    rtCorrectionReferences = NULL,
    method = "polynomial",
    params = list(polynomialOrder = 2),
    robust = FALSE,
    rtWindowWidth = 15,
    diagnostic = TRUE
)

Arguments

annotationObject	(peakPantheRAnnotation) object with previous fit results to adjust retention time values in uROI and FIR annotationObject, rtCorrectionReferences=NULL,
rtCorrectionReferences	(list) of compounds IDs (cpdID) to be used as retention time references. All cpdID entries must be present in the object and previously annotated. If NULL, use all compounds.
method	(str) name of RT correction method to use (currently polynomial or constant
params	(list) list of parameters to pass to each correction method. Currently allowed inputs are polynomialOrder for method='polynomial'
robust	(bool) whether to use the RANSAC algorithm to flag and ignore outliers during retention time correction
rtWindowWidth	(numeric) full width in seconds of the retention time window defined around the corrected retention time value for each compound
diagnostic	(bool) If TRUE returns diagnostic plots (specific to each correction method)

Value

(list) containing entries 'annotation', with the new and retention time corrected peakPantheRAnnotation, and 'plot' (if diagnostic=TRUE).

Examples

if(requireNamespace('faahKO')){
## Initialise a peakPantheRAnnotation object with 3 samples and 2 targeted
## compounds

# Paths to spectra files
library(faahKO)
spectraPaths <- c(system.file('cdf/KO/ko15.CDF', package = 'faahKO'),
                    system.file('cdf/KO/ko16.CDF', package = 'faahKO'))

# targetFeatTable
targetFeatTable <- data.frame(matrix(vector(), 2, 8, dimnames=list(c(),
                    c('cpdID','cpdName','rtMin','rt','rtMax','mzMin','mz',
                    'mzMax'))), stringsAsFactors=FALSE)
targetFeatTable[1,] <- c('ID-1', 'Cpd 1', 3310., 3344.888, 3390., 522.194778,
                        522.2, 522.205222)
targetFeatTable[2,] <- c('ID-2', 'Cpd 2', 3280., 3385.577, 3440., 496.195038,
                        496.2, 496.204962)
targetFeatTable[,c(3:8)] <- vapply(targetFeatTable[,c(3:8)], as.numeric,
                                    FUN.VALUE=numeric(2))

smallAnnotation  <- peakPantheRAnnotation(spectraPaths=spectraPaths,
                                        targetFeatTable=targetFeatTable)
# annotate files serially
annotation_result <- peakPantheR_parallelAnnotation(smallAnnotation,
                                            ncores=0, verbose=TRUE)
data_annotation   <- annotation_result$annotation

# Example with constant correction
rtCorrectionOutput <- retentionTimeCorrection(
                        annotationObject = data_annotation,
                        rtCorrectionReferences=c('ID-1'),
                        method='constant', params=list(),
                        robust=FALSE,
                        rtWindowWidth=15,
                        diagnostic=TRUE)

rtCorrectedAnnotation <- rtCorrectionOutput$annotation

# rtCorrectedAnnotation
# An object of class peakPantheRAnnotation
#  2 compounds in 2 samples.
#  updated ROI exists, with a modified rt (uROI)
#  uses updated ROI (uROI)
#  uses fallback integration regions (FIR)
#  is annotated

rtCorrectionPlot <- rtCorrectionOutput$plot
# rtCorrectedPlot
# A ggplot2 object
#  Scatterplot where x=`r` in the and y=`rt_dev_sec` from data_annotation
#  Points colored depending on whether the reference was used to fit
# the correction model
}

peakPantheR documentation built on Nov. 8, 2020, 6:38 p.m.