drLapply: Apply a function to all key-value pairs of a ddo/ddf object
In datadr: Divide and Recombine for Large, Complex Data

Description Usage Arguments Value Author(s) See Also Examples

Apply a function to all key-value pairs of a ddo/ddf object and get a new ddo object back, unless a different combine strategy is specified.

1 2	drLapply(X, FUN, combine = combDdo(), output = NULL, overwrite = FALSE, params = NULL, packages = NULL, control = NULL, verbose = TRUE)

`X`	an object of class "ddo" of "ddf"
`FUN`	a function to be applied to each subset
`combine`	optional method to combine the results
`output`	a "kvConnection" object indicating where the output data should reside (see `localDiskConn`, `hdfsConn`). If `NULL` (default), output will be an in-memory "ddo" object.
`overwrite`	logical; should existing output location be overwritten? (also can specify `overwrite = "backup"` to move the existing output to _bak)
`params`	a named list of objects external to the input data that are needed in the distributed computing (most should be taken care of automatically such that this is rarely necessary to specify)
`packages`	a vector of R package names that contain functions used in `fn` (most should be taken care of automatically such that this is rarely necessary to specify)
`control`	parameters specifying how the backend should handle things (most-likely parameters to `rhwatch` in RHIPE) - see `rhipeControl` and `localDiskControl`
`verbose`	logical - print messages about what is being done

depends on combine

Ryan Hafen

recombine, drFilter, drJoin, combDdo, combRbind

1 2	bySpecies <- divide(iris, by = "Species") drLapply(bySpecies, function(x) x$Sepal.Width)

*** finding global variables used in 'fn'... [none]
*** testing 'fn' on a subset... ok
* Applying recombination...

Distributed data object backed by 'kvMemory' connection

 attribute      | value
----------------+----------------------------------------------------------------
 size (stored)  | 4.34 KB
 size (object)  | 4.34 KB
 # subsets      | 3

* Other attributes: getKeys()
* Missing attributes: splitSizeDistn