rxArgs: Pass RevoScaleR function arguments

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

Description

The RevoScaleR functions typically have several arguments beyond those used by dplyrXdf verbs. While usually you don't need to touch these, it can sometimes be useful to do so. For example, when using mutate or transmute, you could specify more complicated transformations via a transformFunc. Similarly, rather than chaining together a mutate and a summarise — which would involve creating an intermediate file — you could incorporate the variable transformation into the summarise itself. Most of the one-table dplyrXdf verbs accept an .rxArgs argument as a way of transmitting these extra arguments to the underlying RevoScaleR code. This should be a named list specifying the names and values of the arguments to be passed. The exact arguments will vary depending on the verb in question; here is a list of the verbs and the underlying RevoScaleR function that they call:

• subset, filter and select: rxDataStep

• mutate and transmute: rxDataStep

• summarise: depending on the method chosen, rxCube or rxSummary

• arrange: rxSort

• rename: rxDataStep (only if data movement is required)

• distinct: rxDataStep

• factorise: rxFactors

• doXdf: rxDataStep

• persist: rxDataStep

Details

You should use the .rxArgs argument with caution, as some verbs may modify the data as part of their normal functioning, so the results you get back may not be as expected. It's also easy to write convoluted code that makes your dplyrXdf pipelines harder to read. However, when working with big datasets this feature can help save a lot of processing time by avoiding unnecessary disk traffic.

The following one-table verbs don't support the .rxArgs argument:

• group_by: this verb doesn't do any processing; it only sets things up for subsequent verbs.

• do: the underlying functionality is provided by data frames and dplyr::do.

See Also

rxTransform

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