ffbase: with.ffdf – R documentation

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with.ffdf

Evaluate an expression in a ffdf data environment

Description

Evaluate an R expression in an environment constructed from a ffdf data frame. (see with). Please note that you should write your expression as if it is a normal data.frame. The resulting return value however will be a ff object.

Usage

## S3 method for class 'ffdf'
with(data, expr, ...)

Arguments

`data`	`ffdf` data object used as an environment for evaluation.
`expr`	expression to evaluate.
`...`	arguments to be passed to `chunk`.

Value

if expression is a vector a newly created ff vector will be returned otherwise if the expression is a data.frame a newly created ffdf object will be returned.

Note

'with.ffdf' assumes that the returned object is of equal length as 'nrow(data)' and must be converted to a 'ff' object In case this is not true, the result won't be correct.

Examples

dat <- data.frame(x=1:10, y=10:1)

ffdat <- as.ffdf(dat)

with(ffdat, {x+y})

ffbase

Basic Statistical Functions for Package 'ff'

v0.13.3

GPL-3

Authors

Edwin de Jonge, Jan Wijffels, Jan van der Laan

Initial release