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