read.csv.sql: sqldf's read.csv.sql (no Tcl/tk!)

In alyssafrazee/read.csv.sql: the read.csv.sql function from sqldf, minus the Tcl/tk dependency

Description

Edited version of read.csv.sql in the sqldf package (tcltk functionality removed), used mainly to create a SQLite database from a text file from within R.

Usage

read.csv.sql(file, sql = "select * from file", header = TRUE, sep = ",",
  row.names, eol, skip, filter, nrows, field.types, comment.char,
  dbname = tempfile(), drv = "SQLite", ...)

Arguments

file	A file path or a URL (beginning with http:// or ftp://). If the filter argument is used and no file is to be input to the filter then file can be omitted, NULL, NA or "". The textfile argument from makeDb is used here.
sql	character string holding an SQL statement. The table representing the file should be referred to as file.
header	as in read.csv
sep	as in read.csv
row.names	as in read.csv
eol	Character that ends lines
skip	Skip indicated number of lines in input file.
filter	If specified, this should be a shell/batch command that the input file is piped through.
nrows	Number of rows used to determine column types. It defaults to 50. Using -1 causes it to use all rows for determining column types. This argument is rarely needed.
field.types	A list whose names are the column names and whose contents are the SQLite types (not the R class names) of the columns. Specifying these types improves how fast it takes. Unless speed is very important this argument is not normally used.
comment.char	If specified, this character and anything following it on any line of the input will be ignored.
dbname	As in sqldf except that the default is tempfile(). Specifying NULL will put the database in memory which may improve speed but will limit the size of the database by the available memory. When using tornado, tempfile() is not used: dbname must be provided as an argument to makeDb.
drv	ignored: the only drive used can be SQLite.
...	arguments passed to sqldf.

Details

Reads the indicated file into an sql database creating the database if it does not already exist. Then it applies the sql statement returning the result as a data frame. If the database did not exist prior to this statement it is removed.

Note that it uses facilities of SQLite to read the file which are intended for speed and therefore not as flexible as in R. For example, it does not recognize quoted fields as special but will regard the quotes as part of the field. See the ‘sqldf’ help for more information.

On Windows, if the filter argument is used and if Rtools is detected in the registry, then the Rtools bin directory is added to the search path facilitating use of those tools without explicitly setting any the path.

Value

If the sql statement is a select statement then a data frame is returned.

References

http://cran.r-project.org/web/packages/sqldf/sqldf.pdf

alyssafrazee/read.csv.sql documentation built on May 12, 2019, 2:31 a.m.