minifyMSdata: Shrink MS data by including only data points near masses of...

In RaMS: R Access to Mass-Spec Data

Shrink MS data by including only data points near masses of interest

Description

MS files can be annoyingly large if only a few masses are of interest. This large size makes it difficult to share them online for debugging purposes and often means that untargeted algorithms spend a lot of time picking peaks in data that's irrelevant. minifyMSdata is a function designed to "minify" MS files by extracting only those data points that are within the ppm error of an m/z value of interest, and returns the file essentially otherwise unchanged.

Usage

minifyMSdata(
  files,
  output_files = NULL,
  mz_exclude = NULL,
  mz_include = NULL,
  ppm = NULL,
  warn = TRUE,
  prefilter = -1,
  verbosity = NULL
)

Arguments

files	The name of a single file to be minified, usually produced by Proteowizard's 'msconvert' or something similar.
output_files	The name of the file to be written out.
mz_exclude	A vector of m/z values that should be excluded from the minified file. This argument must be used with the 'ppm' argument and should not be used with mz_include. For each mass provided, an m/z window of +/- 'ppm' is calculated, and all data points within that window are removed.
mz_include	A vector of m/z values that should be included in the minified file. This argument must be used with the 'ppm' argument and should not be used with mz_exclude. For each mass provided, an m/z window of +/- 'ppm' is calculated, and all data points within that window are kept.
ppm	The parts-per-million error of the instrument used to collect the original file.
warn	Boolean. Should the function warn the user when removing an index from an mzML file?
prefilter	A single number corresponding to the minimum intensity of interest in the MS1 data. Data points with intensities below this threshold will be silently dropped, which can dramatically reduce the size of the final object. Currently only works with MS1 data, but could be expanded easily to handle more.
verbosity	A single number with a sensible default behavior. If larger than 2, will render a progress bar as files are processed.

Value

Invisibly, the name of the new files.

Examples

## Not run: 
library(RaMS)
# Extract data corresponding to only valine and homarine
# m/z = 118.0865 and 138.0555, respectively
filename <- system.file("extdata", "LB12HL_AB.mzML.gz", package = "RaMS")
output_filename <- "mini_LB12HL_AB.mzML"
include_mzs <- c(118.0865, 138.0555)
minifyMSdata(filename, output_filename, mz_include=include_mzs, ppm=5)
init_data <- grabMSdata(filename)
mini_data <- grabMSdata(output_filename)
qplotMS1data(rbind(init_data$BPC, mini_data$BPC), color_col = "filename")
unlink(output_filename)

# Exclude data corresponding to valine and homarine
filename <- system.file("extdata", "LB12HL_AB.mzML.gz", package = "RaMS")
output_filename <- "mini_LB12HL_AB.mzML"
exclude_mzs <- c(118.0865, 138.0555)
minifyMSdata(filename, output_filename, mz_exclude=exclude_mzs, ppm=5)
init_data <- grabMSdata(filename)
mini_data <- grabMSdata(output_filename)
qplotMS1data(rbind(init_data$BPC, mini_data$BPC), color_col = "filename")
unlink(output_filename)

## End(Not run)

RaMS documentation built on Oct. 9, 2024, 9:06 a.m.