Update ff content from another object
update copies updates one ff object with the content of another object.
## S3 method for class 'ff'
update(object, from, delete = FALSE, bydim = NULL, fromdim = NULL
, BATCHSIZE = .Machine$integer.max, BATCHBYTES = getOption("ffbatchbytes")
, VERBOSE = FALSE, ...)
## S3 method for class 'ffdf'
update(object, from, ...)object |
an ff object to which to update |
from |
an object from which to uodate |
delete |
NA for quick update with file-exchange, TRUE for quick update with deleting the 'from' object after the update, can speed up updating significantly |
bydim |
how to interpret the content of the object, see |
fromdim |
how to interpret the content of the 'from' object, see |
BATCHSIZE |
|
BATCHBYTES |
|
VERBOSE |
|
... |
further arguments |
If the source object is.ff and not delete=FALSE then instead of slow copying we - if possible - try to swap and rename the files behind the ff objects.
Quick update requires that the two ff objects are vectorCompatible,
that both don't use vw,
that they have identical maxlength
and identical levels.ff.
An ff object like the input 'object' updated with the content of the 'from' object.
You don't have a guarantee that with delete=TRUE the 'from' object gets deleted or with delete=NA the 'from' objects carries the content of 'object'.
Such expectations only turn true if really a quick update was possible.
Jens Oehlschlägel
x <- ff(1:100)
y <- ff(-(1:100))
message("You should make it a habit to re-assign the return value
of update although this is not needed currently.")
x <- update(x, from=y)
x
y
x[] <- 1:100
x <- update(x, from=y, delete=NA)
x
y
x <- update(x, from=y, delete=TRUE)
x
y
x
rm(x,y); gc()
## Not run:
message("timings")
x <- ff(1:10000000)
y <- ff(-(1:10000000))
system.time(update(x, from=y))
system.time(update(y, from=x, delete=NA))
system.time(update(x, from=y, delete=TRUE))
rm(x,y); gc()
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.