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Read file by extension into R.

Usage

import(con, format, text, ...)

# S4 method for character,missing,missing
import(con, format, text, ...)

# S4 method for character,character,missing
import(con, format, text, ...)

# S4 method for DelimFile,missing,missing
import(
  con,
  format,
  text,
  rownames = TRUE,
  rownameCol = NULL,
  colnames = TRUE,
  comment = "",
  skip = 0L,
  nMax = Inf,
  engine = getOption(x = "acid.import.engine", default = "base"),
  makeNames = getOption(x = "acid.import.make.names", default = syntactic::makeNames),
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE),
  verbose = getOption(x = "acid.verbose", default = FALSE)
)

# S4 method for LinesFile,missing,missing
import(
  con,
  format,
  text,
  comment = "",
  skip = 0L,
  nMax = Inf,
  stripWhitespace = FALSE,
  removeBlank = FALSE,
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  engine = getOption(x = "acid.import.engine", default = "base"),
  quiet = getOption(x = "acid.quiet", default = FALSE),
  verbose = getOption(x = "acid.verbose", default = FALSE)
)

# S4 method for ExcelFile,missing,missing
import(
  con,
  format,
  text,
  sheet = 1L,
  rownames = TRUE,
  rownameCol = NULL,
  colnames = TRUE,
  skip = 0L,
  nMax = Inf,
  makeNames = getOption(x = "acid.import.make.names", default = syntactic::makeNames),
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

# S4 method for FASTAFile,missing,missing
import(
  con,
  format,
  text,
  moleculeType = c("DNA", "RNA"),
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

# S4 method for FASTQFile,missing,missing
import(
  con,
  format,
  text,
  moleculeType = c("DNA", "RNA"),
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

# S4 method for GCTFile,missing,missing
import(
  con,
  format,
  text,
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE),
  return = c("matrix", "data.frame")
)

# S4 method for GMTFile,missing,missing
import(con, format, text, quiet = getOption(x = "acid.quiet", default = FALSE))

# S4 method for GMXFile,missing,missing
import(con, format, text, quiet = getOption(x = "acid.quiet", default = FALSE))

# S4 method for GRPFile,missing,missing
import(con, format, text, quiet = getOption(x = "acid.quiet", default = FALSE))

# S4 method for JSONFile,missing,missing
import(
  con,
  format,
  text,
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

# S4 method for MTXFile,missing,missing
import(
  con,
  format,
  text,
  rownamesFile,
  colnamesFile,
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

# S4 method for OBOFile,missing,missing
import(con, format, text, quiet = getOption(x = "acid.quiet", default = FALSE))

# S4 method for PZFXFile,missing,missing
import(
  con,
  format,
  text,
  sheet = 1L,
  makeNames = getOption(x = "acid.import.make.names", default = syntactic::makeNames),
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

# S4 method for YAMLFile,missing,missing
import(
  con,
  format,
  text,
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

# S4 method for RDSFile,missing,missing
import(con, format, text, quiet = getOption(x = "acid.quiet", default = FALSE))

# S4 method for RDataFile,missing,missing
import(con, format, text, quiet = getOption(x = "acid.quiet", default = FALSE))

# S4 method for RioHandoffFile,missing,missing
import(
  con,
  format,
  text,
  rownames = TRUE,
  rownameCol = NULL,
  colnames = TRUE,
  makeNames = getOption(x = "acid.import.make.names", default = syntactic::makeNames),
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE),
  ...
)

# S4 method for RtracklayerHandoffFile,missing,missing
import(
  con,
  format,
  text,
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE),
  ...
)

# S4 method for BcbioCountsFile,missing,missing
import(
  con,
  format,
  text,
  metadata = getOption(x = "acid.import.metadata", default = FALSE),
  quiet = getOption(x = "acid.quiet", default = FALSE)
)

Arguments

con

character(1), connection, or missing. The connection from which data is loaded or to which data is saved. If this is a character vector, it is assumed to be a filename, and a corresponding file connection is created and then closed after exporting the object. If a BiocFile derivative, the data is loaded from or saved to the underlying resource. If missing, the function will return the output as a character vector, rather than writing to a connection.

format

character(1) or missing. An optional file format type, which can be used to override the file format inferred from con. Only recommended for file and URL paths that don't contain an extension.

text

character or missing. Not currently supported.

...

Additional arguments.

rownames

logical(1). Automatically assign row names, if rowname column is defined. Applies to file types that return a data frame only.

rownameCol

NULL, character(1), or integer(1). Applies only when rownames = TRUE. Column name to use for row names assignment. If left NULL (default), the function will call matchRownameCol() internally to attempt to automatically match the row name column (e.g. "rowname" or "rn"). Otherwise, can manually define using a scalar argument, either the name directly or position in the column names.

colnames

logical(1) or character. Automatically assign column names, using the first header row. Applies to file types that return data.frame only. Pass in a character vector to define the column names manually.

comment

character(1). Comment character to detect at beginning of line, which will skip when parsing file. Use "" to disable interpretation of comments, which is particularly useful when parsing lines. Applies to plain text delimited and source code lines only.

skip

integer(1). Number of lines to skip. Applies to delimited file (CSV, TSV), Excel Workbook, or lines.

nMax

integer(1) or Inf. Maximum number of lines to parse. Applies to plain text delimited, Excel, and source code lines only.

engine

character(1). Engine (package) to use for import.

Currently supported:

  • base

  • data.table

  • readr

makeNames

function. Apply syntactic naming function to (column) names. Function is never applied to row names, when they are defined in object.

metadata

list. Metadata.

quiet

logical(1). Perform command quietly, suppressing messages.

verbose

logical(1). Run the function with verbose output.

stripWhitespace

logical(1). Strip leading and/or trailing whitespace. Applies to source code lines.

removeBlank

logical(1). Remove blank lines. Applies to source code lines.

sheet

character(1) or integer(1). Sheet to read. Either a string (the name of a sheet), or an integer (the position of the sheet). Defaults to the first sheet. Applies to Excel Workbook, Google Sheet, or GraphPad Prism file.

moleculeType

character(1). Molecule type, either DNA or RNA. Most RNA-seq FASTQ files contain complementary DNA (cDNA) sequences, not direct sequencing of the RNA molecules.

return

character(1). Object class to return.

rownamesFile, colnamesFile

character(1) or NULL. Row names and/or column names sidecare file. Applies primarily to MatrixMarket Exchange files (e.g. MTXFile).

Value

Varies, depending on the file type (format):

  • Plain text delimited (CSV, TSV, TXT): data.frame.
    Data separated by commas, tabs, or visual spaces.
    Note that TXT structure is amgibuous and actively discouraged.
    Refer to Data frame return section for details on how to change the default return type to DataFrame, tbl_df or data.table.
    Imported by readr::read_delim() by default.

  • Excel workbook (XLSB, XLSX): data.frame.
    Resave in plain text delimited format instead, if possible.
    Imported by readxl::read_excel().

  • Legacy Excel workbook (pre-2007) (XLS): data.frame.
    Resave in plain text delimited format instead, if possible.
    Note that import of files in this format is slow.
    Imported by readxl::read_excel().

  • GraphPad Prism project (PZFX): data.frame.
    Experimental. Consider resaving in CSV format instead.
    Imported by pzfx::read_pzfx().

  • General feature format (GFF, GFF1, GFF2, GFF3, GTF): GenomicRanges.
    Imported by rtracklayer::import().

  • MatrixMarket exchange sparse matrix (MTX): sparseMatrix.
    Imported by Matrix::readMM().

  • Gene cluster text (GCT): matrix or data.frame.
    Imported by readr::read_delim().

  • Gene sets (for GSEA) (GMT, GMX): character.

  • Browser extensible data (BED, BED15, BEDGRAPH, BEDPE): GenomicRanges.
    Imported by rtracklayer::import().

  • ChIP-seq peaks (BROADPEAK, NARROWPEAK): GenomicRanges.
    Imported by rtracklayer::import().

  • Wiggle track format (BIGWIG, BW, WIG): GenomicRanges.
    Imported by rtracklayer::import().

  • JSON serialization data (JSON): list.
    Imported by jsonlite::read_json().

  • YAML serialization data (YAML, YML): list.
    Imported by yaml::yaml.load_file().

  • Lines (LOG, MD, PY, R, RMD, SH): character.
    Source code or log files.
    Imported by readr::read_delim() by default.

  • R data serialized (RDS): variable.
    Currently recommend over RDA, if possible.
    Imported by readRDS().

  • R data (RDA, RDATA): variable.
    Must contain a single object. Doesn't require internal object name to match, unlike loadData().
    Imported by load().

  • Infrequently used rio-compatible formats (ARFF, DBF, DIF, DTA, MAT, MTP, ODS, POR, SAS7BDAT, SAV, SYD, REC, XPT): variable.
    Imported by rio::import().

Details

import() supports automatic loading of common file types, by wrapping popular importer functions. It intentionally designed to be simple, with few arguments. Remote URLs and compressed files are supported. If you need more complex import settings, just call the wrapped importer directly instead.

Note

Updated 2022-11-10.

Row and column names

Row names. Row name handling has become an inconsistent mess in R because of differential support in base R, tidyverse, data.table, and Bioconductor. To maintain sanity, import() attempts to handle row names automatically. The function checks for a rowname column in delimited data, and moves these values into the object's row names, if supported by the return type (e.g. data.frame, DataFrame). Note that tbl_df (tibble) and data.table intentionally do not support row names. When returning in this format, no attempt to assign the rowname column into the return object's row names is made. Note that import() is strict about this matching and only checks for a rowname column, similar to the default syntax recommended in tibble::rownames_to_column(). To disable this behavior, set rownames = FALSE, and no attempt will be made to set the row names.

Column names. import() assumes that delimited files always contain column names. If you are working with a file that doesn't contain column names, either set colnames = FALSE or pass the names in as a character vector. It's strongly recommended to always define column names in a supported file type.

FASTA and FASTQ files

FASTA and FASTQ files are currently managed internally by the Biostrings package. Refer to readDNAStringSet and readRNAStringSet for details. Import of these files will return DNAStringSet or RNAStringSet depending on the input, defined by moleculeType argument.

General feature format (GFF, GTF)

The GFF (General Feature Format) format consists of one line per feature, each containing 9 columns of data, plus optional track definition lines. The GTF (General Transfer Format) is identical to GFF version 2.

See also:

Gene cluster text format (GCT)

Refer to the IGV GCT website for details.

GSEA gene set files

Refer to the Broad Institute GSEA wiki for details.

Matrix Market Exchange

Reading a Matrix Market Exchange file requires ROWNAMES and COLNAMES sidecar files containing the corresponding row and column names of the sparse matrix.

bcbio-nextgen count matrix

bcbio count matrix (e.g. generated from featureCounts) and related sidecar files are natively supported.

  • COUNTS: Counts table (e.g. RNA-seq aligned counts).

  • COLNAMES: Sidecar file containing column names.

  • ROWNAMES: Sidecar file containing row names.

Denylisted extensions

These file formats are intentionally not supported: DOC, DOCX, PDF, PPT, PPTX.

Duplicate methods

GMTFile and OBOFile are also supported by BiocSet package.

Examples

con <- system.file("extdata", "example.csv", package = "pipette")

## Row and column names enabled.
x <- import(con = con)
#> → Importing /private/var/folders/l1/8y8sjzmn15v49jgrqglghcfr0000gn/T/RtmpzEljdg/temp_libpath132762130b79f/pipette/extdata/example.csv using base::`read.table()`.
#>  Setting row names from `rowname` column.
print(head(x))
#>       sample1 sample2 sample3 sample4
#> gene1      16      20      13      16
#> gene2      29      22      43      50
#> gene3     243     245     186     184
#> gene4       7      14      25      16
#> gene5       1       1       2       2
#> gene6      10      17      18      11

## Row and column names disabled.
x <- import(con = con, rownames = FALSE, colnames = FALSE)
#> → Importing /private/var/folders/l1/8y8sjzmn15v49jgrqglghcfr0000gn/T/RtmpzEljdg/temp_libpath132762130b79f/pipette/extdata/example.csv using base::`read.table()`.
print(head(x))
#>        V1      V2      V3      V4      V5
#> 1 rowname sample1 sample2 sample3 sample4
#> 2   gene1      16      20      13      16
#> 3   gene2      29      22      43      50
#> 4   gene3     243     245     186     184
#> 5   gene4       7      14      25      16
#> 6   gene5       1       1       2       2