select: Select columns in a data source

In RevolutionAnalytics/dplyrXdf: Tools for working with Microsoft R Server Xdf files and the dplyr package

Description

Select columns in a data source

Usage

## S3 method for class 'RxFileData'
select(.data, ..., .outFile = tbl_xdf(.data), .rxArgs)

## S3 method for class 'RxDataSource'
select(.data, ...)

Arguments

.data	A data source.
...	Unquoted variables to select.
.outFile	Output format for the returned data. If not supplied, create an xdf tbl; if NULL, return a data frame; if a character string naming a file, save an Xdf file at that location.
.rxArgs	A list of RevoScaleR arguments. See rxArgs for details.

Details

All the special functions mentioned in the documentation for select will also work with dplyrXdf. Note that renaming a variable is not supported in dplyrXdf select. If you want to do this, follow the select with a rename; the latter is very fast, as it only modifies the metadata portion of an xdf file, not the data itself.

Value

An object representing the transformed data. This depends on the .outFile argument: if missing, it will be an xdf tbl object; if NULL, a data frame; and if a filename, an Xdf data source referencing a file saved to that location.

See Also

select in package dplyr, subset

Examples

mtx <- as_xdf(mtcars, overwrite=TRUE)
tbl <- select(mtx, mpg, cyl)
names(tbl)

# filter on rows and columns simultaneously with .rxArgs
tbl2 <- select(mtx, mpg, cyl, .rxArgs=list(rowSelection=am == 1 & vs == 1))
dim(tbl2)

# save to a persistent Xdf file
select(mtx, mpg, cyl, .outFile="mtcars_select.xdf")

RevolutionAnalytics/dplyrXdf documentation built on June 3, 2019, 9:08 p.m.