expanding drSubset output options

[amwhite]

Currently drSubset only allows the result to be returned in memory. It would be helpful if it had the option to save the result using and hdfsConn or localDiskConn (similar to the output parameter in functions such as drLapply, drSample, drFilter, etc).

[hafen]

Yes - I suppose the question is how to partition the results. The purpose of drSubset was to subset the data to a single data frame, in which case why not pull it into memory. If you want to subset the data and maintain the same subsetting, you can simply do it with drLapply. If you want a new partitioning you can do it with addTransform and divide. What do you think?