Package 'mpactr'

LC-MS/MS sample data

Description

A mpactr R6 class object of contining a feature table and associated sample metadata.

Usage

cultures_data

Format

culture_data

A mpactr with 2 attributes:

peak_table

A feature table of class data.table

meta_data

A data.table with associated sample metadata

Value

An mpactr R6 class object.

---

Get file paths for examples

Description

mpactr contains a number of example files in the inst/extdata directory. This function makes them accessible in documentation that shows how file paths are used in function examples.

Usage

example(file = NULL)

Arguments

file	Name of a file. If NULL, all examples files will be listed.

Value

A file path to example data stored in the inst/extdata directory of the package.

Examples

example()

example("metadata.csv")

---

Filter Non-reproducible ions

Description

filter_cv() removes feature ions that are found to be non-reproducible between technical injection replicates. Reproducibility is assessed via mean or median coefficient of variation (CV) between technical replicates. As such, this filter is expecting an input dataset with at least two replicate injections per sample.

copy_object: mpactr is built on an R6 class-system, meaning it operates on reference semantics in which data is updated in-place. Compared to a shallow copy, where only data pointers are copied, or a deep copy, where the entire data object is copied in memory, any changes to the original data object, regardless if they are assigned to a new object, result in changes to the original data object. We recommend using the default copy_object = FALSE as this makes for an extremely fast and memory-efficient way to chain mpactr filters together; however, if you would like to run the filters individually with traditional R style objects, you can set copy_object to TRUE as shown in the filter examples.

Usage

filter_cv(mpactr_object, cv_threshold = NULL, cv_param, copy_object = FALSE)

Arguments

mpactr_object	An mpactr_object. See import_data().
cv_threshold	Coefficient of variation threshold. A lower cv_threshold will result in more stringent filtering and higher reproducibility. Recommended values between 0.2 - 0.5.
cv_param	Coefficient of variation (CV) statistic to use for filtering Options are "mean" or "median", corresponding to mean and median CV, respectively.
copy_object	A boolean parameter that allows users to return a copied object instead of modifying the object.

Value

an mpactr_object.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_cv(data,
  cv_threshold = 0.01,
  cv_param = "mean",
  copy_object = TRUE
)

data_filter <- filter_cv(data,
  cv_threshold = 0.01,
  cv_param = "median",
  copy_object = TRUE
)

---

Filter Ions by Group

Description

Filter Ions by Group

Usage

filter_group(
  mpactr_object,
  group_threshold = 0.01,
  group_to_remove,
  remove_ions = TRUE,
  copy_object = FALSE
)

Arguments

mpactr_object	An mpactr_object. See import_data().
group_threshold	Relative abundance threshold at which to remove ions. Default = 0.01.
group_to_remove	Biological group name to remove ions from.
remove_ions	A boolean parameter. If TRUE failing ions will be removed from the peak table. Default = TRUE.
copy_object	A boolean parameter that allows users to return a copied object instead of modifying the object.

Details

filter_group() removes feature ions that are present in a user-defined group based on a relative abundance threshold. This could be particularly useful to filter out features found present in solvent blank samples. Further, this filter can be ultilized to remove features in media blank sample for experiments on microbial cultures. The presence or absence of features in a group of samples is determined by first averaging injection replicates and then averaging biological replicates within each biological treatment group. A feature is present in a group if its abundance is greater than the user-defined group_threshold. The default is 0.01, meaning a feature is removed if its abundance is 1% of that in the sample group in which it is most abundant. For example, blank filtering can remove features whose mean abundance in solvent blank injections is greater than 1% of their maximum mean abundance in experimental samples.

If you would like to remove features found in media blank samples, we recommend testing the group_threshold parameter.

copy_object: mpactr is built on an R6 class-system, meaning it operates on reference semantics in which data is updated in-place. Compared to a shallow copy, where only data pointers are copied, or a deep copy, where the entire data object is copied in memory, any changes to the original data object, regardless if they are assigned to a new object, result in changes to the original data object. We recommend using the default copy_object = FALSE as this makes for an extremely fast and memory-efficient way to chain mpactr filters together; however, if you would like to run the filters individually with traditional R style objects, you can set copy_object to TRUE as shown in the filter examples.

Value

an mpactr_object.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_group(data,
  group_threshold = 0.01,
  group_to_remove = "Blanks",
  remove_ions = TRUE
)

---

Filter Insource ions

Description

filter_insource_ions() identifies and removes in-source ion clusters based on a Pearson correlation threshold. Groups of co-eluting features with identical retention time are identified and used to generate Pearson correlation matrices. Clusters with self-similarity greater than the user-defined cluster_threshold within these matrices are identified as likely belonging to a single precursor ion and is associated insource ion. Highly correlated ions are identified and removed.

copy_object: mpactr is built on an R6 class-system, meaning it operates on reference semantics in which data is updated in-place. Compared to a shallow copy, where only data pointers are copied, or a deep copy, where the entire data object is copied in memory, any changes to the original data object, regardless if they are assigned to a new object, result in changes to the original data object. We recommend using the default copy_object = FALSE as this makes for an extremely fast and memory-efficient way to chain mpactr filters together; however, if you would like to run the filters individually with traditional R style objects, you can set copy_object to TRUE as shown in the filter examples.

Usage

filter_insource_ions(
  mpactr_object,
  cluster_threshold = 0.95,
  copy_object = FALSE
)

Arguments

mpactr_object	An mpactr_object. See import_data().
cluster_threshold	Cluster threshold for ion deconvolution. Default = 0.95.
copy_object	A boolean parameter that allows users to return a copied object instead of modifying the object.

Value

an mpactr_object

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_insource_ions(data,
  cluster_threshold = 0.95
)

---

Mispicked ions filter

Description

filter_mispicked_ions() identifies ions that were incorrectly split into separate features during preprocessing. This filter checks the feature table for similar ions in terms of mass and retention time. Peaks found to be similar are merged into a single feature given merge_peaks is TRUE.

The parameter ringwin is the detector saturation mass window, specific for some instruments, such as Waters Synapse G2-Si-Q-ToF, to account for high concentration samples.

Parameter isowin is the isotopic mass window, which accounts for isotopic peaks of the same precussor mass that were incorrectly assigned during preprocessing.

copy_object: mpactr is built on an R6 class-system, meaning it operates on reference semantics in which data is updated in-place. Compared to a shallow copy, where only data pointers are copied, or a deep copy, where the entire data object is copied in memory, any changes to the original data object, regardless if they are assigned to a new object, result in changes to the original data object. We recommend using the default copy_object = FALSE as this makes for an extremely fast and memory-efficient way to chain mpactr filters together; however, if you would like to run the filters individually with traditional R style objects, you can set copy_object to TRUE as shown in the filter examples.

Usage

filter_mispicked_ions(
  mpactr_object,
  ringwin = 0.5,
  isowin = 0.01,
  trwin = 0.005,
  max_iso_shift = 3,
  merge_peaks = TRUE,
  merge_method = "sum",
  copy_object = FALSE
)

Arguments

mpactr_object	An mpactr_object. See import_data().
ringwin	Ringing mass window or detector saturation mass window. Default = 0.5 atomic mass units (AMU).
isowin	Isotopic mass window. Default = 0.01 AMU.
trwin	A numeric denoting the retention time threshold for assessing if ions should be merged. Default = 0.005.
max_iso_shift	A numeric. Default = 3.
merge_peaks	A boolean parameter to determine if peaks found to belong to the same ion should be merged in the feature table.
merge_method	If merge_peaks is TRUE, a method for how similar peaks should be merged. Can be one of "sum".
copy_object	A boolean parameter that allows users to return a copied object instead of modifying the object.

Value

an mpactr_object.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_mispicked_ions(data,
  ringwin = 0.5,
  isowin = 0.01,
  trwin = 0.005,
  max_iso_shift = 3,
  merge_peaks = TRUE,
  merge_method = "sum"
)

---

Return the summary for a single mpactr filter.

Description

filter_summary() is a wrapper function to return the summary from a single filter within the given mpactr object.

Usage

filter_summary(mpactr_object, filter, group = NULL)

Arguments

mpactr_object	The mpactr object that is created by calling the import_data() function.
filter	The name of a filter whose summary is to be extracted. Must be one of: "mispicked", "group", "replicability", or "insource".
group	If filter = "group", the name of the Biological_Group used to filter.

Value

a list reporting 1) compound ids for compounds which failed the filter and 2) compound ids for compounds which passed the filter.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_mispicked_ions(data)

mispicked_summary <- filter_summary(data_filter, filter = "mispicked")
mispicked_summary

---

Get CV values.

Description

get_cv_data() is a wrapper function to return cv (coefficient of variation) calculated with filter_cv().

Usage

get_cv_data(mpactr_object)

Arguments

mpactr_object

The mpactr object that is created by calling the import_data() function.

Value

a data.table reporting the mean and median coefficient of variation for each input ion.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_cv(data,
  cv_threshold = 0.01,
  cv_param = "median"
)

cv <- get_cv_data(data_filter)
head(cv)

---

Get groups averages.

Description

get_group_averages() is a wrapper function to return group averages for the filtered peak table.

Usage

get_group_averages(mpactr_object)

Arguments

mpactr_object

The mpactr object that is created by calling the import_data() function.

Value

a data.table reporting the average and relative standard deviation across biological groups and technical replicates within each group.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_group(data, group_to_remove = "Blanks")

group_averages <- get_group_averages(data_filter)
head(group_averages)

---

Return the meta_data data.table from the mpactr object.

Description

get_meta_data() a wrapper function to return the meta data object of the given mpactr object.

Usage

get_meta_data(mpactr_object)

Arguments

mpactr_object

The mpactr object that is created by calling the import_data() function.

Value

a data.table.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

meta_data <- get_meta_data(data)

---

Return the peak table data.table from the mpactr object.

Description

get_peak_table() a wrapper function to return the peak table object of the given mpactr object.

Usage

get_peak_table(mpactr_object)

Arguments

mpactr_object

The mpactr object that is created by calling the import_data() function.

Value

a data.table.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

peak_table <- get_peak_table(data)

---

Return the input peak table from mpactr object.

Description

get_raw_data a wrapper function to return the meta data object of the given mpactr object.

Usage

get_raw_data(mpactr_object)

Arguments

mpactr_object

The mpactr object that is created by calling the import_data() function.

Value

a data.table.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

raw_data <- get_raw_data(data)

---

Get similar ion groups.

Description

get_similar_ions() is a wrapper function to return similar ion groups determined with the filter_mispicked_ions().

Usage

get_similar_ions(mpactr_object)

Arguments

mpactr_object

The mpactr object that is created by calling the import_data() function.

Value

a data.table reporting the main ion and those found to be similar with filter_mispicked_ions().

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_mispicked_ions(data)

mispicked_ion_groups <- get_similar_ions(data_filter)
mispicked_ion_groups

---

Import data into an mpactr object.

Description

import_data() takes two file paths, one for the pre-processed feature table and one for sample metadata. Both files should be .csv.

Usage

import_data(peak_table, meta_data, format = "none")

Arguments

peak_table	The file path or valid https url to your feature table file.
meta_data	The file path to your meta_data file or data.frame.
format	The expected exported type of your peak table, can be one of "Progenesis", "Metaboscape", "None".

Details

mpactr requires a peak table and meta data as input. Files are expected to be comma separated files (.csv).

1. peak_table: a peak table where rows are expected to be compounds. mpactr supports import of feature table files from multiple tools through the format argument. Currently supported value for format are "Progenesis", "Metaboscape", or "None".

format = "Progensis" allows users to provide a feature table exported by Progenesis. To export a compatable peak table in Progenesis, navigate to the Review Compounds tab then File -> Export Compound Measurements. Select the following properties: Compound, m/z, Retention time (min), and Raw abundance and click ok.

format = "Metaboscape" allows users to provide a feature table exported by Metaboscape with default settings. The import function will save the raw peak table in the mpactr_object and store a formatted peak table for filtering. Reformatting includes selecting "FEATURE_ID", "RT", "PEPMASS", and sample columns. Sample columns are determined from the "Injection" column in meta_data (see below). "PEPMASS" is converted to m/z using the "ADDUCT" column and compound metadata columns are renamed for mpactr.

format = "None" allows users to provide a feature table file in the expected format. This can be useful if you have a file from another tool and want to manually format it in R. The table rows are expected to be individual features, while columns are compound metadata and samples. The feature table must have the compound metadata columns "Compound", "mz", and "rt". Where "Compound" is the compound id, and can be numeric or character. "mz" is the compound m/z, and should be numeric. "rt" is the retention time, in mintues, and should be numeric. The remaining columns should be samples, and match the names in the "Injection" column of the meta_data file. 2. meta_data: a table with sample information. Either a file path or data.frame can be supplied. At minimum the following columns are expected: "Injection", "Sample_Code", and "Biological_Group". "Injection" is the sample name and is expected to match sample column names in the peak_table. "Sample_Code" is the id for technical replicate groups. "Biological_Group" is the id for biological replicate groups. Other sample metadata can be added, and is encouraged for downstream analysis following filtering with mpactr.

Value

an mpactr_object.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

meta_data <- read.csv(example("metadata.csv"))
data <- import_data(example("coculture_peak_table.csv"),
  meta_data,
  format = "Progenesis"
)

---

Visualize Filtering Summary as Tree Map

Description

plot_qc_tree() visualizes the filtering summary as a treemap. Ion status (see qc_summary()) is reported here as percentage of all pre-filtered ions.

Usage

plot_qc_tree(mpactr_object)

Arguments

mpactr_object

an mpactr_object.

Value

a tree map plot of class ggplot.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_mispicked_ions(data,
  ringwin = 0.5,
  isowin = 0.01,
  trwin = 0.005,
  max_iso_shift = 3,
  merge_peaks = TRUE
)

plot_qc_tree(data_filter)

---

Summary of Fitering

Description

Parses an mpactr object and exracts a summary of all applied filters. Specifically, the fate of each input ion is reported as ion status. Status options are: Passed, mispicked, group, replicability, and insouce. A status of Passed ions is returned for ions that passed all applied filters and therefore are expected to be high quaility ions. Ions tagged as group, mispicked, replicability, or ionsource were removed during the correspoding filter.

Usage

qc_summary(mpactr_object)

Arguments

mpactr_object

an mpactr_object.

Value

a data.table reporting the number of high quality ions ("Passed") or the filter in which they were removed.

Examples

data <- import_data(example("coculture_peak_table.csv"),
  example("metadata.csv"),
  format = "Progenesis"
)

data_filter <- filter_mispicked_ions(data,
  ringwin = 0.5,
  isowin = 0.01,
  trwin = 0.005,
  max_iso_shift = 3,
  merge_peaks = TRUE
)

summary <- qc_summary(data_filter)
summary

---