readTableIndex

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Reads a single column from file in table format

Usage
## S3 method for class 'default}(..., indexColumn=1, colClass="character", verbose=FALSE)':
readTableIndexundefined

 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().

 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.}

 Returns a vector.

 # 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))

 [object Object]

 readTable().


IO
Aliases
  • readTableIndex.default
  • readTableIndex
Documentation reproduced from package R.utils, version 0.7.9, License: LGPL version 2.1 or newer (the releases)

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