Evaluate an expression in a ffdf data environment
Evaluate an R expression in an environment constructed from a ffdata data frame.
Faster than with.ffdf, but in constrast ffdfwith can change the original data.
Please note that ffdfwith assumes that the result must be of the same length
as nrow(data). You should write
your expression as if it is a normal data.frame. The resulting return value
however will be a ffdf object.
ffdfwith(data, expr, ...)
data |
|
expr |
expression to evaluate. |
... |
arguments to be passed to future methods. |
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.
dat <- data.frame(x=1:10, y=10:1)
ffdat <- as.ffdf(dat)
ffdfwith(ffdat, {
x <- x + 1
x + y
})
#notice that x has been altered
ffdat$xPlease choose more modern alternatives, such as Google Chrome or Mozilla Firefox.