readTableIndex {R.utils} | R Documentation |
Reads a single column from file in table format
Description
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
().
Usage
## Default S3 method:
readTableIndex(..., indexColumn=1, colClass="character", verbose=FALSE)
Arguments
indexColumn |
An single |
colClass |
A single |
... |
Arguments passed to |
verbose |
Value
Returns a vector
.
Author(s)
Henrik Bengtsson
See Also
readTable
().
Examples
## Not run:
# 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))
## End(Not run)
[Package R.utils version 2.12.3 Index]