readTableIndex

0th

Percentile

Reads a single column from file in table format

Reads a single column from file in table format, which can then be used as a index-to-row (look-up) map for fast access to a subset of rows using readTable().

Keywords
IO
Usage
## S3 method for class 'default':
readTableIndex(..., indexColumn=1, colClass="character", verbose=FALSE)
Arguments
indexColumn
An single integer of the index column.
colClass
A single character specifying the class of the index column.
...
Arguments passed to readTable() used internally.
verbose
A logical or a Verbose object.
Value

See Also

readTable().

Aliases
  • readTableIndex.default
  • readTableIndex
Examples
# File containing data table to be access many times
    filename <- "somefile.txt"

    # Create a look-up index
    index <- readTableIndex(filename)

    # Keys of interest
    keys <- c("foo", "bar", "wah")

    # Read only those keys and do it fast
    df <- readTable(filename, rows=match(keys, index))
Documentation reproduced from package R.utils, version 1.6.0, License: LGPL (>= 2.1)

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