alignmentCheck: Verify an alignment by checking the retention time...

In PTXQC: Quality Report Generation for MaxQuant and mzTab Results

Verify an alignment by checking the retention time differences of identical peptides across Raw files

Description

The input is a data frame containing feature evidence with corrected retention times, e.g. a 'calibrated.retention.time' column.

Usage

alignmentCheck(data, referenceFile)

Arguments

data	A data.frame with columns 'calibrated.retention.time', 'id', 'modified.sequence', 'charge', 'raw.file' and 'fraction' (if present)
referenceFile	A raw file name as occuring in data$raw.file, serving as alignment reference (when no fractions are used).

Details

Note that this function must be given real MS/MS identifications only (type "MULTI-MSMS") in order to work correctly!

For each peptide sequence (and charge) in the reference Raw file, this function looks up the already calibrated retention time difference of the same feature in all other files. For every comparison made, we report the RT difference. If alignment worked perfectly, the differences are very small (<1 min).

An 'id' column must be present, to enable mapping the result of this function to the original data frame.

A reference Raw file can be identified using 'findAlignReference()'. If Maxquants experimental design included pre-fractionation, a column named 'fraction' should be given and 'referenceFile' should be empty. This function will pick the one Raw file for each fraction (the first in order) to use as reference. Only the immediately neighbouring fractions will be matched to this reference.

Value

A data.frame containing the RT diff for each feature found in a Raw file and the reference.

PTXQC documentation built on July 26, 2023, 5:27 p.m.