indexing: Indexing SQLiteDataset Objects

In dfdb: Access Data Tables in a SQLite Data Base as Pseudo-Dataframes

Description

Methods for indexing SQLiteDataset Objects. The [ method can take a quoted SQL query as its “row” argument.

Usage

## S3 method for class 'SQLiteDataset'
x[[i]]
## S3 method for class 'SQLiteDataset'
x[i, j, drop = TRUE, ...]
## S3 method for class 'SQLiteDataset'
x$i

Arguments

x	an SQLiteDataset object.
i	for [[ and $, a column name or number; for [, a quoted SQL query to select rows from the data set.
j	a vector of quoted column names or of column numbers.
drop	if TRUE (the default) and only one column is selected, return a vector.
...	ignored.

Value

a data frame or vector.

Note

An empty subscript returns all rows or columns; to select the entire data set, specify dsname[].

Author(s)

John Fox, [e-mail].

See Also

SQLiteDataset, $

Examples

dr <- dbDriver("SQLite")
tfile <- tempfile()
con <- dbConnect(dr, dbname = tfile)
dbWriteTable(con, "USArrests", USArrests)
dbDisconnect(con)
Arrests <- SQLiteDataset("USArrests", database=tfile)
Arrests$Murder
Arrests[["Murder"]]
Arrests["Murder > 10", c("Murder", "Rape")]
close(Arrests)

dfdb documentation built on May 2, 2019, 4:58 p.m.