Dynamic combine() is now dynamic group()

[wlandau]

Summary

As @dpmccabe and @JodyStats mentioned in #1064 and #1065, dynamic combine() is confusing because it covers both splitting and aggregation. group() really fits both, so I am changing the name. If you try to use combine(), you get an informative error.

library(drake)
library(magrittr)

plan <- drake_plan(
  data = mtcars,
  cyl = data$cyl,
  
  # splitting. Works with and without `.by`.
  subsets = target(
    data,
    dynamic = combine(data, .by = cyl)
  ),
  
  # aggregation. Works with and without `.by`.
  cars_per_cyl = target(
    purrr::map_int(subsets, nrow),
    dynamic = group(subsets)
  )
)

make(plan)
#> Error: Dynamic combine() does not exist. use group() instead. Ref: https://github.com/ropensci/drake/issues/1065

^{Created on 2019-11-14 by the reprex package (v0.3.0)}

Intended usage:

library(drake)
library(magrittr)

plan <- drake_plan(
  data = mtcars,
  cyl = data$cyl,
  
  # splitting
  subsets = target(
    data,
    dynamic = group(data, .by = cyl)
  ),
  
  # aggregation
  cars_per_cyl = target(
    purrr::map_int(subsets, nrow),
    dynamic = group(subsets)
  )
)

make(plan)
#> target data
#> target cyl
#> dynamic subsets
#> subtarget subsets_895749a8
#> subtarget subsets_503adfac
#> subtarget subsets_9278e453
#> aggregate subsets
#> dynamic cars_per_cyl
#> subtarget cars_per_cyl_736d8ea8
#> aggregate cars_per_cyl

readd(subsets) %>%
  setNames(read_trace("cyl", "subsets"))
#> [[1]]
#>                 mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#> Mazda RX4      21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
#> Mazda RX4 Wag  21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
#> Hornet 4 Drive 21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
#> Valiant        18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1
#> Merc 280       19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4
#> Merc 280C      17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4
#> Ferrari Dino   19.7   6 145.0 175 3.62 2.770 15.50  0  1    5    6
#> 
#> [[2]]
#>                 mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#> Datsun 710     22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1
#> Merc 240D      24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2
#> Merc 230       22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2
#> Fiat 128       32.4   4  78.7  66 4.08 2.200 19.47  1  1    4    1
#> Honda Civic    30.4   4  75.7  52 4.93 1.615 18.52  1  1    4    2
#> Toyota Corolla 33.9   4  71.1  65 4.22 1.835 19.90  1  1    4    1
#> Toyota Corona  21.5   4 120.1  97 3.70 2.465 20.01  1  0    3    1
#> Fiat X1-9      27.3   4  79.0  66 4.08 1.935 18.90  1  1    4    1
#> Porsche 914-2  26.0   4 120.3  91 4.43 2.140 16.70  0  1    5    2
#> Lotus Europa   30.4   4  95.1 113 3.77 1.513 16.90  1  1    5    2
#> Volvo 142E     21.4   4 121.0 109 4.11 2.780 18.60  1  1    4    2
#> 
#> [[3]]
#>                      mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#> Hornet Sportabout   18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
#> Duster 360          14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4
#> Merc 450SE          16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3
#> Merc 450SL          17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3
#> Merc 450SLC         15.2   8 275.8 180 3.07 3.780 18.00  0  0    3    3
#> Cadillac Fleetwood  10.4   8 472.0 205 2.93 5.250 17.98  0  0    3    4
#> Lincoln Continental 10.4   8 460.0 215 3.00 5.424 17.82  0  0    3    4
#> Chrysler Imperial   14.7   8 440.0 230 3.23 5.345 17.42  0  0    3    4
#> Dodge Challenger    15.5   8 318.0 150 2.76 3.520 16.87  0  0    3    2
#> AMC Javelin         15.2   8 304.0 150 3.15 3.435 17.30  0  0    3    2
#> Camaro Z28          13.3   8 350.0 245 3.73 3.840 15.41  0  0    3    4
#> Pontiac Firebird    19.2   8 400.0 175 3.08 3.845 17.05  0  0    3    2
#> Ford Pantera L      15.8   8 351.0 264 4.22 3.170 14.50  0  1    5    4
#> Maserati Bora       15.0   8 301.0 335 3.54 3.570 14.60  0  1    5    8

readd(cars_per_cyl)
#> [[1]]
#> [1]  7 11 14

^{Created on 2019-11-14 by the reprex package (v0.3.0)}

Related GitHub issues and pull requests

• Ref: Confuse with the meaning of combine() #1065

Checklist

• I understand and agree to drake's code of conduct.
• I have listed any substantial changes in the development news.
• I have added testthat unit tests to tests/testthat for any new functionality.
• This pull request is not a draft.

[codecov-io]

Codecov Report

Merging #1068 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #1068   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files          47      47           
  Lines        7289    7294    +5     
======================================
+ Hits         7289    7294    +5

Impacted Files	Coverage Δ
R/drake_config.R	100% <ø> (ø)	⬆️
R/manage_memory.R	100% <ø> (ø)	⬆️
R/drake_plan_helpers.R	100% <ø> (ø)	⬆️
R/transform_plan.R	100% <ø> (ø)	⬆️
R/make.R	100% <ø> (ø)	⬆️
R/dynamic.R	100% <100%> (ø)	⬆️
R/create_drake_layout.R	100% <100%> (ø)	⬆️

---

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[lintr-bot]

R/dynamic.R:431:1: style: Lines should not be more than 80 characters.

​match_dynamic_call_impl.map <- match_dynamic_call_impl.cross <- function(dynamic) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

R/dynamic.R:435:1: style: Variable and function names should not be longer than 30 characters.

​match_dynamic_call_impl.combine <- function(dynamic) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~