importFFDF: Import a file to flat file data.frame (FFDF)

In CALIBERdatamanage: Data Management Tools for CALIBER Datasets

Description

Imports a a text file or multiple files to FFDF, automatically converting dates.

Usage

importFFDF(filename, datecolnames = NULL,
    verbose = TRUE, sep = NULL, zipname = NULL,
    nrowcheck = 30, fread = FALSE, ...)

Arguments

filename	a single filename or vector of filenames or path to a text file, gz compressed text file or a zip file containing one file. If multiple files are to be loaded, they must all have columns in the same order with the same data types and the same column names.
datecolnames	which columns to cenvert to Date or IDate. It can be either a vector of date column names, or an empty string (for no dates to be converted) or NULL if an attempt should be made to convert all columns. Columns which cannot be coerced to date are left unchanged. Non-missing dates are not permitted.
verbose	whether to print information about the file loaded.
sep	a single delimiter character. If NULL, the function will try to detect it (, ; or TAB) from the first line.
zipname	path to a zip file. This is only required if the zip file contains more than one file, otherwise the path to the zip file can be supplied as the filename argument. If multi = TRUE, zipname can be vector of paths to multiple zip files.
nrowcheck	number of rows checked to determine the data type when loading chunkwise
fread	whether to use data.table's fread function for loading data
...	other arguments to pass to read.delim

Value

a FFDF (flat file data frame) object. This is a dataset stored physically on the hard drive, with a hybrid index in RAM so that elements can be accessed quickly.

Author(s)

Anoop Shah

See Also

importDT, extractEntity, as.data.table.ffdf

Examples

# Import a test dataset
data(test_data)
tempfile <- paste(tempdir(), '/tmp.csv', sep='')
write.csv(test_data, tempfile, row.names = FALSE)
importFFDF(tempfile)

# Convert to data.table
as.data.table(importFFDF(tempfile))

# Importing multiple datasets
for (enttype in c(1, 4, 5, 21, 151)){
    write.csv(test_data[test_data$enttype == enttype, ],
        paste(tempfile, enttype, sep=''), row.names = FALSE)
}
importFFDF(paste(tempfile, c(1, 4, 5, 21, 151), sep = ''))

# Clean up
unlink(tempfile)

CALIBERdatamanage documentation built on Nov. 23, 2021, 3 p.m.