readr (version 0.2.0)

read_fwf: Read a fixed width file.

Description

A fixed width file can be a very compact representation of numeric data. It's also very fast to parse, because every field is in the same place in every line. Unfortunately, it's painful to parse because you need to describe the length of every field. Readr aims to make it as easy as possible by providing a number of different ways to describe the field structure.

Usage

read_fwf(file, col_positions, col_types = NULL, locale = default_locale(), na = c("", "NA"), skip = 0, n_max = -1, progress = interactive())
fwf_empty(file, skip = 0, col_names = NULL)
fwf_widths(widths, col_names = NULL)
fwf_positions(start, end, col_names = NULL)

Arguments

file

Either a path to a file, a connection, or literal data (either a single string or a raw vector).

Files ending in .gz, .bz2, .xz, or .zip will be automatically uncompressed. Files starting with http://, https://, ftp://, or ftps:// will be automatically downloaded. Remote gz files can also be automatically downloaded & decompressed.

Literal data is most useful for examples and tests. It must contain at least one new line to be recognised as data (instead of a path).

col_positions

Column positions, as created by fwf_empty, fwf_widths or fwf_positions. To read in only selected fields, use fwf_positions. The width of the last column will be silently extended to the next line break.

col_types

One of NULL, a cols, specification of a string. See vignette("column-types") for more details.

If NULL, all column types will be imputed from the first 1000 rows on the input. This is convenient (and fast), but not robust. If the imputation fails, you'll need to supply the correct types yourself.

If a column specification created by cols, it must contain one "collector" for each column. If you only want to read a subset of the columns, use cols_only.

Alternatively, you can use a compact string representation where each character represents one column: c = character, i = integer, n = number, d = double, l = logical, D = date, T = date time, t = time, ? = guess, or _/- to skip the column.

locale

The locale controls defaults that vary from place to place. The default locale is US-centric (like R), but you can use locale to create your own locale that controls things like the default time zone, encoding, decimal mark, big mark, and day/month names.

na

Character vector of strings to use for missing values. Set this option to character() to indicate no missing values.

skip

Number of lines to skip before reading data.

n_max

Maximum number of records to read.

progress

Display a progress bar? By default it will only display in an interactive session. The display is updated every 50,000 values and will only display if estimated reading time is 5 seconds or more.

col_names

Either NULL, or a character vector column names.

widths

Width of each field.

start, end

Starting and ending (inclusive) positions of each field.

See Also

read_table to read fixed width files where each column is separated by whitespace.

Examples

fwf_sample <- system.file("extdata/fwf-sample.txt", package = "readr")
cat(read_lines(fwf_sample))

# You can specify column positions in three ways:
# 1. Guess based on position of empty columns
read_fwf(fwf_sample, fwf_empty(fwf_sample))
# 2. A vector of field widths
read_fwf(fwf_sample, fwf_widths(c(2, 5, 3)))
# 3. Paired vectors of start and end positions
read_fwf(fwf_sample, fwf_positions(c(1, 4), c(2, 10)))