Add support for dplyr ungroup()

[ianmcook]

Would it be possible to add support for the dplyr verb ungroup()? When using the verb group_by() it is often a best practice to explicitly call ungroup() after, but it looks like ungroup() is not currently implemented in disk.frame. Thanks!

[xiaodaigh]

Thanks for the report. The implementation is as follow :), and has been added here. If you use the latest master and chunk_ungroup. Let me know if there are more issues.

chunk_ungroup = create_dplyr_mapper(dplyr::ungroup)

At some point, I will write an article explaining how create_dplyr_mapper works. Any dplyr function can be created this way, using the create_dplyr_mapper.

[xiaodaigh]

iris %>% 
  as.disk.frame(nchunks = 2) %>% 
  chunk_group_by(Species) %>% 
  chunk_ungroup %>% 
  collect

this seems to work in the latest "development" branch

[ianmcook]

With the support for group_by() in disk.frame 0.3.0, could you please add support for ungroup() (without the chunk_ prefix)? Thanks!