Zooming to a table of a dm allows for the use of many dplyr-verbs directly on this table, while retaining the
context of the dm object.
dm_zoom_to() zooms to the given table.
dm_update_zoomed() overwrites the originally zoomed table with the manipulated table.
The filter conditions for the zoomed table are added to the original filter conditions.
dm_insert_zoomed() adds a new table to the dm.
dm_discard_zoomed() discards the zoomed table and returns the dm as it was before zooming.
Please refer to vignette("tech-db-zoom", package = "dm")
for a more detailed introduction.
dm_zoom_to(dm, table) dm_insert_zoomed(dm, new_tbl_name = NULL, repair = "unique", quiet = FALSE) dm_update_zoomed(dm) dm_discard_zoomed(dm)
| dm | A |
|---|---|
| table | A table in the |
| new_tbl_name | Name of the new table. |
| repair | Either a string or a function. If a string, it must
be one of
The |
| quiet | By default, the user is informed of any renaming
caused by repairing the names. This only concerns unique and
universal repairing. Set |
For dm_zoom_to(): A zoomed_dm object.
For dm_insert_zoomed(), dm_update_zoomed() and dm_discard_zoomed(): A dm object.
Whenever possible, the key relations of the original table are transferred to the resulting table
when using dm_insert_zoomed() or dm_update_zoomed().
Functions from dplyr that are supported for a zoomed_dm: group_by(), summarise(), mutate(),
transmute(), filter(), select(), rename() and ungroup().
You can use these functions just like you would
with a normal table.
In addition to filtering the zoomed table, the filter condition from filter() is also stored in the dm.
Depending on which function you use to return to a normal dm, one of the following happens:
dm_discard_zoomed(): all filter conditions for the zoomed table are discarded
dm_update_zoomed(): the filter conditions of the original table and those of the zoomed table are combined
dm_insert_zoomed(): the filter conditions of the original table stay there and those of the zoomed table are
transferred to the new table of the dm
Furthermore, the different join()-variants from dplyr are also supported (apart from nest_join()).
The join-methods for zoomed_dm have an extra argument select that allows choosing the columns of the RHS table.
And -- last but not least -- also the tidyr-functions unite() and separate() are supported for zoomed_dm.
#> # Zoomed table: flights #> # A tibble: 11,227 x 19 #> year month day dep_time sched_dep_time dep_delay arr_time sched_arr_time #> <int> <int> <int> <int> <int> <dbl> <int> <int> #> 1 2013 1 10 3 2359 4 426 437 #> 2 2013 1 10 16 2359 17 447 444 #> 3 2013 1 10 450 500 -10 634 648 #> 4 2013 1 10 520 525 -5 813 820 #> 5 2013 1 10 530 530 0 824 829 #> 6 2013 1 10 531 540 -9 832 850 #> 7 2013 1 10 535 540 -5 1015 1017 #> 8 2013 1 10 546 600 -14 645 709 #> 9 2013 1 10 549 600 -11 652 724 #> 10 2013 1 10 550 600 -10 649 703 #> # … with 11,217 more rows, and 11 more variables: arr_delay <dbl>, #> # carrier <chr>, flight <int>, tailnum <chr>, origin <chr>, dest <chr>, #> # air_time <dbl>, distance <dbl>, hour <dbl>, minute <dbl>, time_hour <dttm>flights_zoomed_transformed <- flights_zoomed %>% mutate(am_pm_dep = ifelse(dep_time < 1200, "am", "pm")) %>% # `by`-argument of `left_join()` can be explicitly given # otherwise the key-relation is used left_join(airports) %>% select(year:dep_time, am_pm_dep, everything()) flights_zoomed_transformed#> # Zoomed table: flights #> # A tibble: 11,227 x 27 #> year month day dep_time am_pm_dep sched_dep_time dep_delay arr_time #> <int> <int> <int> <int> <chr> <int> <dbl> <int> #> 1 2013 1 10 3 am 2359 4 426 #> 2 2013 1 10 16 am 2359 17 447 #> 3 2013 1 10 450 am 500 -10 634 #> 4 2013 1 10 520 am 525 -5 813 #> 5 2013 1 10 530 am 530 0 824 #> 6 2013 1 10 531 am 540 -9 832 #> 7 2013 1 10 535 am 540 -5 1015 #> 8 2013 1 10 546 am 600 -14 645 #> 9 2013 1 10 549 am 600 -11 652 #> 10 2013 1 10 550 am 600 -10 649 #> # … with 11,217 more rows, and 19 more variables: sched_arr_time <int>, #> # arr_delay <dbl>, carrier <chr>, flight <int>, tailnum <chr>, origin <chr>, #> # dest <chr>, air_time <dbl>, distance <dbl>, hour <dbl>, minute <dbl>, #> # time_hour <dttm>, name <chr>, lat <dbl>, lon <dbl>, alt <dbl>, tz <dbl>, #> # dst <chr>, tzone <chr># replace table `flights` with the zoomed table flights_zoomed_transformed %>% dm_update_zoomed()#> ── Metadata ──────────────────────────────────────────────────────────────────── #> Tables: `airlines`, `airports`, `flights`, `planes`, `weather` #> Columns: 61 #> Primary keys: 3 #> Foreign keys: 3# insert the zoomed table as a new table flights_zoomed_transformed %>% dm_insert_zoomed("extended_flights") %>% dm_draw()# discard the zoomed table flights_zoomed_transformed %>% dm_discard_zoomed()#> ── Metadata ──────────────────────────────────────────────────────────────────── #> Tables: `airlines`, `airports`, `flights`, `planes`, `weather` #> Columns: 53 #> Primary keys: 3 #> Foreign keys: 3