Package 'MIC'

Description

Calculate the bias between two AMR::mic vectors. The bias is calculated as the percentage of test MICs that are above the gold standard MICs minus the percentage of test MICs that are below the gold standard MICs.

Usage

bias(gold_standard, test)

Arguments

Value

numeric value

References

International Organization for Standardization. ISO 20776-2:2021 Available from: https://www.iso.org/standard/79377.html

Examples

gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
bias(gold_standard, test)

Description

Removes leading "=" which can sometimes be present in raw MIC results. Also converts co-trimoxazole to trimethprim component only.

Usage

clean_raw_mic(mic)

Arguments

Value

character of clean MIC/s

Examples

clean_raw_mic(c("==>64","0.25/8.0"))

Description

This function reorganises files that have been split into train and test directories using train_test_filesystem() back into a single directory. This is a convenience function to reverse the effects of train_test_filesystem().

Usage

combined_file_system(
  path_to_folders,
  file_ext,
  train_folder = "train",
  test_folder = "test",
  overwrite = FALSE
)

Arguments

Value

Logical vector, indicated success or failure for each file

Examples

set.seed(123)
# create 10 random DNA files
tmp_dir <- tempdir()
# remove any existing .fna files
file.remove(
 list.files(tmp_dir, pattern = "*.fna", full.names = TRUE)
)
for (i in 1:10) {
writeLines(paste0(">", i, "\n", paste0(sample(c("A", "T", "C", "G"),
  100, replace = TRUE), collapse = "")), file.path(tmp_dir, paste0(i, ".fna")))
}

# split files into train and test directories
paths <- train_test_filesystem(tmp_dir,
                               file_ext = "fna",
                               split = 0.8,
                               shuffle = TRUE,
                               overwrite = TRUE)
# combine files back into a single directory
combined_file_system(tmp_dir, "fna")
list.files(tmp_dir)

Description

This function compares an vector of MIC values to another. Generally, this is in the context of a validation experiment – an investigational assay or method (the "test") is compared to a gold standard. The rules used by this function are in line with "ISO 20776-2:2021 Part 2: Evaluation of performance of antimicrobial susceptibility test devices against reference broth micro-dilution."

There are two levels of detail that are provided. If only the MIC values are provided, the function will look for essential agreement between the two sets of MIC. If the organism and antibiotic arguments are provided, the function will also calculate the categorical agreement using EUCAST breakpoints (or, if breakpoint not available and accept_ecoff = TRUE, ECOFFs).

The function returns a special dataframe of results, which is also an mic_validation object. This object can be summarised using summary() for summary metrics, plotted using plot() for an essential agreement confusion matrix, and tabulated using table().

Usage

compare_mic(
  gold_standard,
  test,
  ab = NULL,
  mo = NULL,
  accept_ecoff = FALSE,
  simplify = TRUE
)

Arguments

Value

S3 mic_validation object

Examples

# Just using MIC values only
gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
val <- compare_mic(gold_standard, test)
summary(val)

# Using MIC values and antibiotic and organism names
gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
ab <- c("AMK", "AMK", "AMK", "AMK")
mo <- c("B_ESCHR_COLI", "B_ESCHR_COLI", "B_ESCHR_COLI", "B_ESCHR_COLI")
val <- compare_mic(gold_standard, test, ab, mo)
"error" %in% names(val)  # val now has categorical agreement

Description

Compare two AMR::sir vectors and generate a categorical agreement vector with the following levels: M (major error), vM (very major error), m (minor error). The error definitions are:

1. Major error (M): The test result is resistant (R) when the gold standard is susceptible (S).

2. vM (very major error): The test result is susceptible (S) when the gold standard is resistant (R).

3. Minor error (m): The test result is intermediate (I) when the gold standard is susceptible (S) or resistant (R), or vice versa.

Usage

compare_sir(gold_standard, test)

Arguments

Value

factor vector with the following levels: M, vM, m.

Examples

gold_standard <- c("S", "R", "I", "I")
gold_standard <- AMR::as.sir(gold_standard)
test <- c("S", "I", "R", "R")
test <- AMR::as.sir(test)
compare_sir(gold_standard, test)

Description

Download PATRIC database

Usage

download_patric_db(save_path, ftp_path = patric_ftp_path, overwrite = FALSE)

Arguments

Value

TRUE if successful, FALSE if failure.

Examples

download_patric_db(tempfile())

Description

A dataset containing the epidemiological cut-off values (ECOFFs) for different antibiotics and microorganisms. Currently, only the ECOFF values for Escherichia coli are included.

Usage

ecoffs

Format

ecoffs

A data frame with 85 rows and 25 columns:

organism

Microorganism code in AMR::mo format

antibiotic

Antibiotic code in AMR::ab format

0.002:512

Counts of isolates in each concentration "bin"

Distributions

see EUCAST documentation below

Observations

Number of observations

⁠(T)ECOFF⁠

see EUCAST documentation below

⁠Confidence interval⁠

see EUCAST documentation below

Source

EUCAST https://www.eucast.org/mic_and_zone_distributions_and_ecoffs

These data have (or this document, presentation or video has) been produced in part under ECDC service contracts and made available by EUCAST at no cost to the user and can be accessed on the EUCAST website www.eucast.org. The views and opinions expressed are those of EUCAST at a given point in time. EUCAST recommendations are frequently updated and the latest versions are available at www.eucast.org.

Description

Essential agreement calculation for comparing two MIC vectors.

Usage

essential_agreement(x, y, coerce_mic = TRUE, mode = "categorical")

Arguments

Details

Essential agreement is a central concept in the comparison of two sets of MIC values. It is most often used when validating a new method against a gold standard. This function reliably performs essential agreement in line with ISO 20776-2:2021. The function can be used in two modes: categorical and numeric. In categorical mode, the function will use traditional MIC concentrations to determine the MIC (therefore it will use force_mic() to convert both x and y to a clean MIC – see ?force_mic()). In numeric mode, the function will compare the ratio of the two MICs. In most cases, categorical mode provides more reliable results. Values within +/- 2 dilutions are considered to be in essential agreement.

Value

logical vector

References

International Organization for Standardization. ISO 20776-2:2021 Available from: https://www.iso.org/standard/79377.html

Examples

x <- AMR::as.mic(c("<0.25", "8", "64", ">64"))
y <- AMR::as.mic(c("<0.25", "2", "16", "64"))
essential_agreement(x, y)
# TRUE FALSE FALSE TRUE

Description

Example minimum inhibitory concentration validation data for three antimicrobials on Escherichia coli strains. This data is synthetic and generated to give an example of different MIC distribution.

Usage

example_mics

Format

example_mics

A data frame with 300 rows and 4 columns:

gs

Gold standard MICs

test

Test MICs

mo

Microorganism code in AMR::mo format

ab

Antibiotic code in AMR::ab format

Source

Synthetic data

Description

Fill MIC dilution levels

Usage

fill_dilution_levels(x, cap_upper = TRUE, cap_lower = TRUE, as.mic = TRUE)

Arguments

Value

ordered factor (or AMR::mic if as.mic = TRUE)

Examples

# use in combination with droplevels to clean up levels:
x <- AMR::as.mic(c("<0.25", "8", "64", ">64"))
x <- droplevels(x)
fill_dilution_levels(x)

Description

Convert a value that is "almost" an MIC into a valid MIC value.

Usage

force_mic(
  value,
  levels_from_AMR = FALSE,
  max_conc = 512,
  min_conc = 0.002,
  method = "closest",
  prefer = "max"
)

Arguments

Details

Some experimental or analytical conditions measure MIC (or surrogate) in a way that does not fully conform to traditional MIC levels (i.e., concentrations). This function allows these values to be coerced into an MIC value that is compatible with the AMR::mic class. When using method = "closest", the function will choose the closest MIC value to the input value (e.g., 2.45 will be coerced to 2). When using method = "round up", the function will round up to the next highest MIC value (e.g., 2.45 will be coerced to 4). "Round up" is technically the correct approach if the input value was generated from an experiment that censored between concentrations (e.g., broth or agar dilution). However, "closest" may be more appropriate in some cases.

Value

AMR::as.mic compatible character

Examples

force_mic(c("2.32", "<4.12", ">1.01"))

Description

This function converts a single genome to a libsvm file containing kmer counts. The libsvm format will be as follows:

  label 1:count 2:count 3:count ...

Label is optional and defaults to 0. The kmer counts are indexed by the kmer index, which is the lexicographically sorted index of the kmer. Libsvm is a sparse format.

Usage

genome_to_libsvm(
  x,
  target_path,
  label = as.character(c("0")),
  k = 3L,
  canonical = TRUE,
  squeeze = FALSE
)

Arguments

Value

boolean indicating success

See Also

For multiple genomes in a directory, processed in parallel, see genomes_to_kmer_libsvm()

For more details on libsvm format, see https://xgboost.readthedocs.io/en/stable/tutorials/input_format.html

Examples

temp_libsvm_path <- tempfile(fileext = ".txt")
genome_to_libsvm("ATCGCAGT", temp_libsvm_path)
readLines(temp_libsvm_path)

Description

Raw genome data (pre- or post-assembly) is usually transformed by k-mer counting prior to machine learning (ML). XGBoost is a popular ML algorithm for this problem, due to its scalability to high dimensional data. This function converts genomes to k-mer counts stored in XGBoost's preferred format, libsvm. Further information on the libsvm format is available at https://xgboost.readthedocs.io/en/stable/tutorials/input_format.html. Briefly, libsvm is effectively a text file that stores data points as x:y pairs, where x is the feature index, and y is the feature value. Each observation is stored on its own line, with the first column reserved for labels. Labels can be provided later, during data import.

This function converts each individual genome to an individual libsvm text file of k-mer counts (therefore, each .txt file will be 1 line long). This function supports parallel processing using the by setting an appropriate future::plan() (usually future::multisession) — each genome is processed in parallel. To monitor progress, use the progressr package by wrapping the function in with_progress.

Although XGBoost can load a multiple .txt (libsvm) files by providing the directory as an input, this is generally not recommended as order of import cannot be guaranteed and probably depends on filesystem. Instead, it is recommended that this function is combined with split_and_combine_files() which generates a single .txt file (with the order of observations guaranteed and stored in a .csv file).

Usage

genomes_to_kmer_libsvm(
  source_dir,
  target_dir,
  k = 3,
  canonical = TRUE,
  squeeze = FALSE,
  ext = ".fna"
)

Arguments

Value

TRUE if successful

See Also

to convert a single genome, use genome_to_libsvm()

Examples

set.seed(123)
# create 10 random DNA files
tmp_dir <- tempdir()
# remove any existing .fna files
file.remove(
 list.files(tmp_dir, pattern = "*.fna", full.names = TRUE)
)
for (i in 1:10) {
writeLines(paste0(">", i, "\n", paste0(sample(c("A", "T", "C", "G"),
 100, replace = TRUE), collapse = "")), file.path(tmp_dir, paste0(i, ".fna")))
}

tmp_target_dir <- file.path(tmp_dir, "kmers")
unlink(tmp_target_dir, recursive = TRUE)

# convert genomes to k-mers
future::plan(future::sequential)  # use multisession for parallel processing
progressr::with_progress(
  genomes_to_kmer_libsvm(tmp_dir, tmp_target_dir, k = 3)
)

# check the output
list.files(tmp_target_dir)
readLines(list.files(tmp_target_dir, full.names = TRUE)[1])

Description

This function helps extract MICs from a database of results. It is compatible with the PATRIC meta data format when used on a tidy_patric_db object, created using tidy_patric_db().

If more than one MIC is present for a particular observation, the function can return the higher MIC by setting prefer_high_mic = TRUE. If prefer_high_mic = FALSE, the lower MIC will be returned.

Usage

get_mic(
  x,
  ids,
  ab_col,
  id_col = NULL,
  as_mic = TRUE,
  prefer_high_mic = TRUE,
  simplify = TRUE
)

Arguments

Value

vector containing MICs, or dataframe of IDs and MICs

Examples

df <- data.frame(genome_id = c("a_12", "b_42", "x_21", "x_21", "r_75"),
                 gentamicin = c(0.25, 0.125, 32.0, 16.0, "<0.0125"))
get_mic(df,
        ids = c("b_42", "x_21"),
        ab_col = "gentamicin",
        id_col = "genome_id",
        as_mic = FALSE,
        prefer_high_mic = TRUE,
        simplify = TRUE)

Description

Generates genome kmers

Usage

kmers(
  x,
  k = 3L,
  simplify = FALSE,
  canonical = TRUE,
  squeeze = FALSE,
  anchor = TRUE,
  clean_up = TRUE,
  key_as_int = FALSE,
  starting_index = 1L
)

Arguments

Value

list of kmer values, either as a list of a single vector (if simplify = TRUE), or as a named list containing "kmer_string" and "kmer_value".

Examples

kmers("ATCGCAGT")

Description

Load PATRIC database

Usage

load_patric_db(x = patric_ftp_path)

Arguments

Value

PATRIC database (S3 class 'patric_db')

Examples

patric_db <- load_patric_db()  # will get from PATRIC ftp


# make data.frame with single row
p <- data.frame(genome_id = 1,
                genome_name = "E. coli",
                antibiotic = "amoxicillin",
                measurement = 2.0,
                measurement_unit = "mg/L",
                laboratory_typing_method = "Agar dilution",
                resistant_phenotype = "R")
load_patric_db(p)

Description

MIC datasets often arise from different laboratories or experimental conditions. In practice, this means that there can be different levels of censoring (<= and >) within the data. This function can be used to harmonise the dataset to a single level of censoring. The function requires a set of rules that specify the censoring levels (see example).

Usage

mic_censor(mic, ab, mo, rules)

Arguments

Value

censored MIC values (S3 mic class)

Examples

example_rules <- list("B_ESCHR_COLI" = list(
  "AMK" = list(min = 2, max = 32),
  "CHL" = list(min = 4, max = 64),
  "GEN" = list(min = 1, max = 16),
  "CIP" = list(min = 0.015, max = 4),
  "MEM" = list(min = 0.016, max = 16),
  "AMX" = list(min = 2, max = 64),
  "AMC" = list(min = 2, max = 64),
  "FEP" = list(min = 0.5, max = 64),
  "CAZ" = list(min = 1, max = 128),
  "TGC" = list(min = 0.25, max = 1)
  ))

mic_censor(AMR::as.mic(512),
           "AMK",
           "B_ESCHR_COLI",
           example_rules) == AMR::as.mic(">32")

Description

R breakpoint for MIC

Usage

mic_r_breakpoint(mo, ab, accept_ecoff = FALSE, ...)

Arguments

Value

MIC value

Examples

mic_r_breakpoint("B_ESCHR_COLI", "AMK")
mic_r_breakpoint("B_ESCHR_COLI", "CHL", accept_ecoff = TRUE)

Description

Generate dilution series

Usage

mic_range(start = 512, dilutions = Inf, min = 0.002, precise = FALSE)

Arguments

Value

Vector of numeric concentrations

Examples

mic_range(128)
mic_range(128, dilutions = 21) # same results

Description

S breakpoint for MIC

Usage

mic_s_breakpoint(mo, ab, accept_ecoff = FALSE, ...)

Arguments

Value

MIC value

Examples

mic_s_breakpoint("B_ESCHR_COLI", "AMK")
mic_s_breakpoint("B_ESCHR_COLI", "CHL", accept_ecoff = TRUE)

Description

Uncensor MICs

Usage

mic_uncensor(
  mic,
  method = "scale",
  scale = 2,
  ab = NULL,
  mo = NULL,
  distros = NULL
)

Arguments

Details

Censored MIC data is generally unsuitable for modelling without some conversion of censored data. The default behaviour (method = scale) is to halve MICs under the limit of detection (<=) and double MICs above the limit of detection (>). When used with method = simple, this function effectively just removes the censoring symbols, e.g., <=2 becomes 2, and >64 becomes 64.

The bootstrap method is the more complex of the three available methods. It attempts to use a second (uncensored) MIC distribution to sample values in the censored range. These values are then used to populate and uncensor the MIC data provided as input (mic). The second (uncensored) MIC distribution is ideally provided from similar experimental conditions. Alternatively, epidemiological distributions can be used. These distributions should be provided as a dataframe to the distros argument. The format for this dataframe is inspired by the EUCAST epidemiological distributions, see: https://www.eucast.org/mic_and_zone_distributions_and_ecoffs. The dataframe should contain columns for antimicrobial (converted using AMR::as.ab), organism (converted using AMR::as.mo), and MIC concentrations. An example is provided in the 'ecoffs' dataset available with this pacakge. Currently, only Escherichia coli is available in this dataset. Each observation (row) consists of the frequency a particular MIC concentration is observed in the distribution. If such a dataframe is not provided to distros, the function will attempt to use 'ecoffs', but remains limited to E. coli.

Value

vector of MICs in AMR::mic format

References

https://www.eucast.org/mic_and_zone_distributions_and_ecoffs

Examples

mic_uncensor(c(">64.0", "<0.25", "8.0"), method = "scale", scale = 2)

Description

This is simply a wrapper around file.copy/file.rename that allows for filtering by a logical vector (move_which). This can replicate the behaviour of a predicate function (see example), and may be easier to read.

Usage

move_files(source_dir, target_dir, move_which, ext = ".txt", copy = FALSE)

Arguments

Value

Logical vector, indicating success or failure for each file

Examples

set.seed(123)
# create 10 random DNA files
tmp_dir <- tempdir()
# remove any existing .fna files
file.remove(
 list.files(tmp_dir, pattern = "*.fna", full.names = TRUE)
)
for (i in 1:10) {
writeLines(paste0(">", i, "\n", paste0(sample(c("A", "T", "C", "G"),
 100, replace = TRUE), collapse = "")), file.path(tmp_dir, paste0(i, ".fna")))
}

# move files with even numbers to a new directory
new_dir <- file.path(tempdir(), "even_files")
unlink(new_dir, recursive = TRUE)
move_files(tmp_dir,
           new_dir,
           move_which = as.integer(
              tools::file_path_sans_ext(
                  list.files(tmp_dir, pattern = "*.fna"))) %% 2 == 0,
           ext = "fna")
list.files(new_dir)

Description

Plot MIC validation results

Usage

## S3 method for class 'mic_validation'
plot(
  x,
  match_axes = TRUE,
  add_missing_dilutions = TRUE,
  facet_wrap_ncol = NULL,
  facet_wrap_nrow = NULL,
  ...
)

Arguments

Value

ggplot object

Examples

gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
val <- compare_mic(gold_standard, test)
plot(val)

# works with validation that includes categorical agreement
# categorical agreement is ignored
ab <- c("AMK", "AMK", "AMK", "AMK")
mo <- c("B_ESCHR_COLI", "B_ESCHR_COLI", "B_ESCHR_COLI", "B_ESCHR_COLI")
val <- compare_mic(gold_standard, test, ab, mo)
plot(val)

# if the validation contains multiple antibiotics, i.e.,
ab <- c("CIP", "CIP", "AMK", "AMK")
val <- compare_mic(gold_standard, test, ab, mo)
# the following will plot all antibiotics in a single plot (pooled results)
plot(val)
# use the faceting arguments to split the plot by antibiotic
plot(val, facet_wrap_ncol = 2)

Description

Print MIC validation object

Usage

## S3 method for class 'mic_validation'
print(x, ...)

Arguments

Value

character

Examples

gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
val <- compare_mic(gold_standard, test)
print(val)

Description

Print MIC validation summary

Usage

## S3 method for class 'mic_validation_summary'
print(x, ...)

Arguments

Value

character

Examples

gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
val <- compare_mic(gold_standard, test)
print(summary(val))

Description

Automated download of genomes from PATRIC database

Usage

pull_PATRIC_genomes(
  output_directory,
  taxonomic_name = NULL,
  database = patric_ftp_path,
  filter = "MIC",
  n_genomes = 0
)

Arguments

Value

The number of failed downloads (i.e., 0 if all attempted downloads were successful).

Examples

pull_PATRIC_genomes(tempdir(),
                    taxonomic_name = "Escherichia coli",
                    filter = "MIC",
                    n_genomes = 10)

Description

Check whether MIC values are within acceptable range for quality control (QC). Every MIC experiment should include a control strain with a known MIC. The results of the experiment are only valid if the control strain MIC falls within the acceptable range. This function checks whether an MIC result is within the acceptable range given: 1) a control strain (usually identified as an ATCC or NCTC number), 2) an antibiotic name, and 3) a guideline (EUCAST or CLSI). The acceptable range is defined by 'QC_table', which is a dataset which is loaded with this package.

The source of the QC values is the WHONET QC Ranges and Targets available from the 'Antimicrobial Resistance Test Interpretation Engine' (AMRIE) repository: https://github.com/AClark-WHONET/AMRIE

Usage

qc_in_range(
  measurement,
  strain,
  ab,
  ignore_na = TRUE,
  guideline = "EUCAST",
  year = "2023"
)

Arguments

Value

logical vector

References

O’Brien TF, Stelling JM. WHONET: An Information System for Monitoring Antimicrobial Resistance. Emerg Infect Dis. 1995 Jun;1(2):66–66.

Examples

qc_in_range(AMR::as.mic(0.5), 25922, "GEN") == TRUE
qc_in_range(AMR::as.mic(8.0), 25922, "GEN") == FALSE

Check that QC measurement is at the required target

Description

MIC experiments should include a control strain with a known MIC. The MIC result for the control strain should be a particular target MIC. This function checks whether the target MIC was achieved given: 1) a control strain (usually identified as an ATCC or NCTC number), 2) an antibiotic name, and 3) a guideline (EUCAST or CLSI).

Since QC target values are currently not publicly available in an easy to use format, this function takes a pragmatic approach – for most antibiotics and QC strains, the target is assumed to be the midpoint of the acceptable range. This approximation is not necessarily equal to the QC target reported by guideline setting bodies such as EUCAST. Therefore, this function is considered experimental and should be used with caution.

This function can be used alongnside qc_in_range(), which checks whether the MIC is within the acceptable range.

The source of the QC values is the WHONET QC Ranges and Targets available from the 'Antimicrobial Resistance Test Interpretation Engine' (AMRIE) repository: https://github.com/AClark-WHONET/AMRIE

Usage

qc_on_target(
  measurement,
  strain,
  ab,
  ignore_na = TRUE,
  guideline = "EUCAST",
  year = "2023"
)

Arguments

Value

logical vector

References

O’Brien TF, Stelling JM. WHONET: An Information System for Monitoring Antimicrobial Resistance. Emerg Infect Dis. 1995 Jun;1(2):66–66.

Examples

qc_on_target(AMR::as.mic(0.5), 25922, "GEN") == TRUE

Description

Removes multiple slashes in a path or url

Usage

replace_multiple_slashes(path)

Arguments

Value

character vector of paths without duplicate slashes

Description

Reverse complement of DNA string

Usage

reverse_complement(dna)

Arguments

Value

reverse complement of DNA string

Examples

reverse_complement("ATCG")

Description

This function combines files into a train and test set, stored on disk. It can be used in combination with genomes_to_kmer_libsvm() to create a dataset that can be loaded into XGBoost (either by first creating an xgboost::DMatrix, or by using the data argument in xgboost::xgb.train() or xgboost::xgb.cv()). The following three files will be created:

1. train.txt - the training data

2. test.txt - the testing data (if split < 1)

3. names.csv - a csv file containing the original filenames and their corresponding type (train or test)

The function will check if the data is already in the appropriate format and will not overwrite unless forced using the overwrite argument.

By providing 1.0 to the split argument, the function can be used to combine files without a train-test split. In this case, all the files will be classed as 'train', and there will be no 'test' data. This is useful if one wants to perform cross-validation using xgboost::xgb.cv() or MIC::xgb.cv.lowmem(). It is also possible to combine all data into train and then perform splitting after loading into an xgboost::DMatrix, using xgboost::slice().

Usage

split_and_combine_files(
  path_to_files,
  file_ext = ".txt",
  split = 0.8,
  train_target_path = NULL,
  test_target_path = NULL,
  names_backup = NULL,
  shuffle = TRUE,
  overwrite = FALSE
)

Arguments

Value

named list of paths to created train/test files, original filenames

Examples

set.seed(123)
# create 10 random libsvm files
tmp_dir <- tempdir()
# remove any existing .txt files
file.remove(
list.files(tmp_dir, pattern = "*.txt", full.names = TRUE)
)
for (i in 1:10) {
 # each line is K: V
 writeLines(paste0(i, ": ", paste0(sample(1:100, 10, replace = TRUE),
 collapse = " ")), file.path(tmp_dir, paste0(i, ".txt")))
 }

 # split files into train and test directories
 paths <- split_and_combine_files(
  tmp_dir,
  file_ext = "txt",
  split = 0.8,
  train_target_path = file.path(tmp_dir, "train.txt"),
  test_target_path = file.path(tmp_dir, "test.txt"),
  names_backup = file.path(tmp_dir, "names.csv"),
  overwrite = TRUE)

 readLines(paths[["train"]])

Description

Get str conversion of squeezed kmer using index

Usage

squeezed_index_to_str(x, k, starting_index = 1L)

Arguments

Value

vector of squeezed kmer strings

Examples

squeezed_index_to_str(2, k = 3)

Description

Generates all permutations of squeezed kmers

Usage

squeezed_mers(k = 3L)

Arguments

Value

vector of squeezed kmers

Examples

squeezed_mers(3)

Standardise MIC to control strain

Description

MIC experiments are generally quality-controlled by including a control strain with a known MIC. The MIC result for the control strain should be a particular target MIC, or at least within an acceptable range. This function standardises a measured MIC to the target MIC given: 1) a control strain (usually identified as an ATCC or NCTC number), 2) an antibiotic name, and 3) a guideline (EUCAST or CLSI). The definition of standardisation in this context is to adjust the measured MIC based on the QC MIC. This is based on the following principles and assumption:

1. A measured MIC is composed of two components: the true MIC and a measurement error. The measurement error is considered to be inevitable when measuring MICs, and is likely to be further composed of variability in laboratory conditions and operator interpretation.

2. It is assumed that the MIC of the control strain in the experiment has also been affected by this error.

The standardisation applied by this function uses the measured QC strain MIC as a reference point, and scales the rest of the MICs to this reference. In general, this means that the MICs are doubled or halved, depending on the result of the QC MIC. A worked example is provided below and illustrates the transformation that this function applies.

There is no current evidence base for this approach, therefore, this function is considered experimental and should be used with caution.

Usage

standardise_mic(
  test_measurement,
  qc_measurement,
  strain,
  ab,
  prefer_upper = FALSE,
  ignore_na = TRUE,
  guideline = "EUCAST",
  year = "2023",
  force = TRUE
)

Arguments

Value

AMR::mic vector

Examples

# Ref strain QC MIC for GEN is 0.5
standardise_mic(
  test_measurement = c(AMR::as.mic(">8.0"),  # QC = 1, censored MIC remains censored
                       AMR::as.mic(4.0),  # QC = 0.5 which is on target, so stays same
                       AMR::as.mic(2),  # QC = 1, so scaled down to 1
                       AMR::as.mic(2)),  # QC = 0.25, so scaled up to 8
  qc_measurement = c(AMR::as.mic(1),
                     AMR::as.mic(0.5),
                     AMR::as.mic(1),
                     AMR::as.mic(0.25)),
  strain = 25922,
  ab = AMR::as.ab("GEN"))

Description

Summarise the results of an MIC validation generated using compare_mic().

Usage

## S3 method for class 'mic_validation'
summary(object, ...)

Arguments

Value

S3 mic_validation_summary object

Examples

gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
val <- compare_mic(gold_standard, test)
summary(val)
# or, for more detailed results
as.data.frame(summary(val))

Description

Table

Usage

table(x, ...)

## Default S3 method:
table(x, ...)

## S3 method for class 'mic_validation'
table(
  x,
  format = "flextable",
  fill_dilutions = TRUE,
  bold = TRUE,
  ea_color = NULL,
  gold_standard_name = "Gold Standard",
  test_name = "Test",
  ...
)

Arguments

Value

table or flextable object

Examples

gold_standard <- c("<0.25", "8", "64", ">64")
test <- c("<0.25", "2", "16", "64")
val <- compare_mic(gold_standard, test)
table(val)

Description

Tidy PATRIC data

Usage

tidy_patric_meta_data(
  x,
  prefer_more_resistant = TRUE,
  as_ab = TRUE,
  filter_abx = NULL
)

Arguments

Value

Tidy data, with antimicrobials in wide format, column names describing methodology ("mic_", "disk_", "pheno_"). S3 class "tidy_patric_db".

Examples

db <- data.frame(genome_id = 1,
                genome_name = "E. coli",
                antibiotic = "amoxicillin",
                measurement = 2.0,
                measurement_unit = "mg/L",
                laboratory_typing_method = "Agar dilution",
                resistant_phenotype = "R")
db <- load_patric_db(db)
tidy_patric_meta_data(db)

Description

Organise files into a train-test filesystem

Usage

train_test_filesystem(
  path_to_files,
  file_ext,
  split = 0.8,
  train_folder = "train",
  test_folder = "test",
  shuffle = TRUE,
  overwrite = FALSE
)

Arguments

Value

named vector of train and test directories

Examples

set.seed(123)
# create 10 random DNA files
tmp_dir <- tempdir()
# remove any existing .fna files
file.remove(
  list.files(tmp_dir, pattern = "*.fna", full.names = TRUE)
)

for (i in 1:10) {
 writeLines(paste0(">", i, "\n", paste0(sample(c("A", "T", "C", "G"),
 100, replace = TRUE), collapse = "")), file.path(tmp_dir, paste0(i, ".fna")))
}

# split files into train and test directories
paths <- train_test_filesystem(tmp_dir,
                               file_ext = "fna",
                               split = 0.8,
                               shuffle = TRUE,
                               overwrite = TRUE)

list.files(paths[["train"]])
list.files(paths[["test"]])

Description

Get str conversion of unsqueezed kmer using index

Usage

unsqueezed_index_to_str(x, k, starting_index = 1L)

Arguments

Value

vector of unsqueezed kmer strings

Examples

unsqueezed_index_to_str(2, k = 3)

Description

Generates all permutations of unsqueezed kmers

Usage

unsqueezed_mers(k = 3L)

Arguments

Value

vector of unsqueezed kmers

Examples

unsqueezed_mers(3)

Description

This function performs similar operations to xgboost::xgb.cv, but with the operations performed in a memory efficient manner. Unlike xgboost::xgb.cv, this version does not load all folds into memory from the start. Rather it loads each fold into memory sequentially, and trains trains each fold using xgboost::xgb.train. This allows larger datasets to be cross-validated.

The main disadvantage of this function is that it is not possible to perform early stopping based the results of all folds. The function does accept an early stopping argument, but this is applied to each fold separately. This means that different folds can (and should be expected to) train for a different number of rounds.

This function also allows for a train-test split (as opposed to multiple) folds. This is done by providing a value of less than 1 to nfold, or a list of 1 fold to folds. This is not possible with xgboost::xgb.cv, but can be desirable if there is downstream processing that depends on an xgb.cv.synchromous object (which is the return object of both this function and xgboost::xgb.cv).

Otherwise, where possible this function tries to return the same data structure as xgboost::xgb.cv, with the exception of callbacks (not supported as a field within the return object). To save models, use the save_models argument, rather than the cb.cv.predict(save_models = TRUE) callback.

Usage

xgb.cv.lowmem(
  params = list(),
  data,
  nrounds,
  nfold,
  label = NULL,
  missing = NA,
  prediction = FALSE,
  metrics = list(),
  obj = NULL,
  feval = NULL,
  stratified = TRUE,
  folds = NULL,
  train_folds = NULL,
  verbose = 1,
  print_every_n = 1L,
  early_stopping_rounds = NULL,
  maximize = NULL,
  save_models = FALSE,
  ...
)

Arguments

Value

xgb.cv.synchronous object

Examples

train <- list(data = matrix(rnorm(20), ncol = 2),
             label = rbinom(10, 1, 0.5))
dtrain <- xgboost::xgb.DMatrix(train$data, label = train$label, nthread = 1)
cv <- xgb.cv.lowmem(data = dtrain,
                   params = list(objective = "binary:logistic"),
                   nrounds = 2,
                   nfold = 3,
                   prediction = TRUE,
                   nthread = 1)
cv