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extract_tables

Source: R/extract_tables.R
extract_tables.Rd

Extract tables from a file

Usage

extract_tables(
  file,
  pages = NULL,
  area = NULL,
  columns = NULL,
  guess = TRUE,
  method = c("decide", "lattice", "stream"),
  output = c("matrix", "data.frame", "character", "asis", "csv", "tsv", "json"),
  outdir = NULL,
  password = NULL,
  encoding = NULL,
  copy = FALSE,
  ...
)

Arguments

file

A character string specifying the path or URL to a PDF file.

pages

An optional integer vector specifying pages to extract from.

area

An optional list, of length equal to the number of pages specified, where each entry contains a four-element numeric vector of coordinates (top,left,bottom,right) containing the table for the corresponding page. As a convenience, a list of length 1 can be used to extract the same area from all (specified) pages. Only specify area or columns. Warning: area is ignored if guess is TRUE.

columns

An optional list, of length equal to the number of pages specified, where each entry contains a numeric vector of horizontal (x) coordinates separating columns of data for the corresponding page. As a convenience, a list of length 1 can be used to specify the same columns for all (specified) pages. Only specify area or columns. Warning: columns is ignored if guess is TRUE.

guess

A logical indicating whether to guess the locations of tables on each page. If FALSE, area or columns must be specified; if TRUE, area and columns are ignored.

method

A string identifying the preferred method of table extraction.

  • method = "decide" (default) automatically decide (for each page) whether spreadsheet-like formatting is present and "lattice" is appropriate

  • method = "lattice" use Tabula's spreadsheet extraction algorithm

  • method = "stream" use Tabula's basic extraction algorithm

output

A function to coerce the Java response object (a Java ArrayList of Tabula Tables) to some output format. The default method, “matrices”, returns a list of character matrices. See Details for other options.

outdir

Output directory for files if output is set to "csv", "tsv" or "json", ignored otherwise. If equals NULL (default), uses R sessions temporary directory tempdir().

password

Optionally, a character string containing a user password to access a secured PDF.

encoding

Optionally, a character string specifying an encoding for the text, to be passed to the assignment method of Encoding.

copy

Specifies whether the original local file(s) should be copied to tempdir() before processing. FALSE by default. The argument is ignored if file is URL.

...

These are additional arguments passed to the internal functions dispatched by method.

Value

By default, a list of character matrices. This can be changed by specifying an alternative value of method (see Details).

Details

This function mimics the behavior of the Tabula command line utility. It returns a list of R character matrices containing tables extracted from a file by default. This response behavior can be changed by using the following options.

  • output = "character" returns a list of single-element character vectors, where each vector is a tab-delimited, line-separate string of concatenated table cells.

  • output = "data.frame" attempts to coerce the structure returned by method = "character" into a list of data.frames and returns character strings where this fails.

  • output = "csv" writes the tables to comma-separated (CSV) files using Tabula's CSVWriter method in the same directory as the original PDF. method = "tsv" does the same but with tab-separated (TSV) files using Tabula's TSVWriter and method = "json" does the same using Tabula's JSONWriter method. Any of these three methods return the path to the directory containing the extract table files.

  • output = "asis" returns the Java object reference, which can be useful for debugging or for writing a custom parser.

extract_areas implements this functionality in an interactive mode allowing the user to specify extraction areas for each page.

References

Tabula

See also

extract_areas, get_page_dims, make_thumbnails, split_pdf

Author

Thomas J. Leeper <[email protected]>, Tom Paskhalis <[email protected]>

Examples

if (FALSE) {
# simple demo file
f <- system.file("examples", "data.pdf", package = "tabulizer")

# extract all tables
extract_tables(f)

# extract tables from only second page
extract_tables(f, pages = 2)

# extract areas from a page
## full table
extract_tables(f, pages = 2, area = list(c(126, 149, 212, 462)))
## part of the table
extract_tables(f, pages = 2, area = list(c(126, 284, 174, 417)))

# return data.frames
extract_tables(f, pages = 2, output = "data.frame")
}