Migration guide: ‘cdm’ -> ‘dm’

Replace cdm with dm

During this update the prevalent prefix cdm was discarded in favor of dm. The old prefix would still do its job, but a warning message would be issued each time a function beginning with cdm was being used, informing that the function is soft-deprecated and suggesting the use of its newer version.

If you have a script which is based on an older {dm} version, it should still work with the newer version, albeit complaining each time an outdated function is being used. This can be repaired by:

1. either going through the script step by step, testing the output of each line of code and use the new function names provided in the generated warnings to update the function calls.
2. or just by replacing all occurrences of cdm by dm in this script. This can e.g. be done in RStudio using “Find” or in the terminal using sed -e 's/cdm/dm/g' path-to-file on Windows or sed -i '' -e 's/cdm/dm/g' path-to-file on a Mac. If the script errors after this step, you will need to check where exactly the error happens and manually repair the damage.

Be careful with methods for dm: tbl, [[, $

Furthermore, you need to pay attention if you used one of tbl.dm(), [[.dm(), $.dm(). During the same update the implementation for those methods changed as well, and here you don’t get the convenient warning messages. The change was, that before the update, the mentioned methods would return the table after “filtering” it to just contain the rows with values that relate via foreign key relations to other tables that were filtered earlier. After the update just the table as is would be returned. If you want to retain the former behavior, you need to replace each of the methods with the function dm_apply_filters_to_tbl(), which was made available with the update.

The methods are of course not to be avoided in general, if no filters are set anyway the result will not change after the update.

Here a short example for the different cases:

Formerly you would access the “filtered” tables using the following syntax:

library(dm)
flights_dm <- dm_nycflights13()
tbl(flights_dm, "airports")

#> # A tibble: 1,458 x 8
#>    faa   name                    lat    lon   alt    tz dst   tzone        
#>    <chr> <chr>                 <dbl>  <dbl> <dbl> <dbl> <chr> <chr>        
#>  1 04G   Lansdowne Airport      41.1  -80.6  1044    -5 A     America/New_…
#>  2 06A   Moton Field Municipa…  32.5  -85.7   264    -6 A     America/Chic…
#>  3 06C   Schaumburg Regional    42.0  -88.1   801    -6 A     America/Chic…
#>  4 06N   Randall Airport        41.4  -74.4   523    -5 A     America/New_…
#>  5 09J   Jekyll Island Airport  31.1  -81.4    11    -5 A     America/New_…
#>  6 0A9   Elizabethton Municip…  36.4  -82.2  1593    -5 A     America/New_…
#>  7 0G6   Williams County Airp…  41.5  -84.5   730    -5 A     America/New_…
#>  8 0G7   Finger Lakes Regiona…  42.9  -76.8   492    -5 A     America/New_…
#>  9 0P2   Shoestring Aviation …  39.8  -76.6  1000    -5 U     America/New_…
#> 10 0S9   Jefferson County Intl  48.1 -123.    108    -8 A     America/Los_…
#> # … with 1,448 more rows

flights_dm$planes

#> # A tibble: 3,322 x 9
#>    tailnum  year type       manufacturer  model  engines seats speed engine
#>    <chr>   <int> <chr>      <chr>         <chr>    <int> <int> <int> <chr> 
#>  1 N10156   2004 Fixed win… EMBRAER       EMB-1…       2    55    NA Turbo…
#>  2 N102UW   1998 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#>  3 N103US   1999 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#>  4 N104UW   1999 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#>  5 N10575   2002 Fixed win… EMBRAER       EMB-1…       2    55    NA Turbo…
#>  6 N105UW   1999 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#>  7 N107US   1999 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#>  8 N108UW   1999 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#>  9 N109UW   1999 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#> 10 N110UW   1999 Fixed win… AIRBUS INDUS… A320-…       2   182    NA Turbo…
#> # … with 3,312 more rows

flights_dm[["weather"]]

#> # A tibble: 861 x 15
#>    origin  year month   day  hour  temp  dewp humid wind_dir wind_speed
#>    <chr>  <int> <int> <int> <int> <dbl> <dbl> <dbl>    <dbl>      <dbl>
#>  1 EWR     2013     1    10     0  41    32    70.1      230       8.06
#>  2 EWR     2013     1    10     1  39.0  30.0  69.9      210       9.21
#>  3 EWR     2013     1    10     2  39.0  28.9  66.8      230       6.90
#>  4 EWR     2013     1    10     3  39.9  27.0  59.5      270       5.75
#>  5 EWR     2013     1    10     4  41    26.1  55.0      320       6.90
#>  6 EWR     2013     1    10     5  41    26.1  55.0      300      12.7 
#>  7 EWR     2013     1    10     6  39.9  25.0  54.8      280       6.90
#>  8 EWR     2013     1    10     7  41    25.0  52.6      330       6.90
#>  9 EWR     2013     1    10     8  43.0  25.0  48.7      330       8.06
#> 10 EWR     2013     1    10     9  45.0  23    41.6      320      17.3 
#> # … with 851 more rows, and 5 more variables: wind_gust <dbl>,
#> #   precip <dbl>, pressure <dbl>, visib <dbl>, time_hour <dttm>

After the update the same result is achieved by this type of function call:

dm_apply_filters_to_tbl(flights_dm, airlines)

#> # A tibble: 16 x 2
#>    carrier name                       
#>    <chr>   <chr>                      
#>  1 9E      Endeavor Air Inc.          
#>  2 AA      American Airlines Inc.     
#>  3 AS      Alaska Airlines Inc.       
#>  4 B6      JetBlue Airways            
#>  5 DL      Delta Air Lines Inc.       
#>  6 EV      ExpressJet Airlines Inc.   
#>  7 F9      Frontier Airlines Inc.     
#>  8 FL      AirTran Airways Corporation
#>  9 HA      Hawaiian Airlines Inc.     
#> 10 MQ      Envoy Air                  
#> 11 OO      SkyWest Airlines Inc.      
#> 12 UA      United Air Lines Inc.      
#> 13 US      US Airways Inc.            
#> 14 VX      Virgin America             
#> 15 WN      Southwest Airlines Co.     
#> 16 YV      Mesa Airlines Inc.