dplyr 0.8.1

Introduction#

We’re delighted to announce the release of dplyr 0.8.1 on CRAN 🎉 !

This is a minor release that address follow ups from the community after the release of the 0.8.0 version .

group_map() and group_modify()#

Shortly after the release of 0.8.0, we were notified by several members of the community that group_map() was great, except it didn’t do what they had expected 😬.

Because the function was (and still is) marked as experimental, we allowed ourselves to rectify the situation:

The name group_map() is now used for iterating on groups of grouped tibbles, characterised by .x and .y as before, but making no assumptions about the return type of each operation and combining the results in a list. We can see this as iterating, in the purrr::map() sense on the groups.

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library(dplyr, warn.conflicts = FALSE)

# a list of vectors
iris %>%
  group_by(Species) %>%
  group_map(~ quantile(.x$Petal.Length, probs = c(0.25, 0.5, 0.75)))
#> [[1]]
#>   25%   50%   75% 
#> 1.400 1.500 1.575 
#> 
#> [[2]]
#>  25%  50%  75% 
#> 4.00 4.35 4.60 
#> 
#> [[3]]
#>   25%   50%   75% 
#> 5.100 5.550 5.875

The behaviour we previously had was renamed group_modify() to loosely echo purrr::modify() . In particular, group_modify() always returns a grouped tibble, which combines the tibbles returned by evaluating each operation with a reconstructed grouping structure.

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# to use group_modify() the lambda must return a data frame
iris %>%
  group_by(Species) %>%
  group_modify(~ {
     quantile(.x$Petal.Length, probs = c(0.25, 0.5, 0.75)) %>%
     tibble::enframe(name = "prob", value = "quantile")
  })
#> # A tibble: 9 x 3
#> # Groups:   Species [3]
#>   Species    prob  quantile
#>   <fct>      <chr>    <dbl>
#> 1 setosa     25%       1.4 
#> 2 setosa     50%       1.5 
#> 3 setosa     75%       1.58
#> 4 versicolor 25%       4   
#> 5 versicolor 50%       4.35
#> 6 versicolor 75%       4.6 
#> 7 virginica  25%       5.1 
#> 8 virginica  50%       5.55
#> 9 virginica  75%       5.88

Attention to details in column wise functions#

As we are phasing funs() out and prefer use of purrr-style lambda functions in column wise verbs, we missed a few subtleties.

Specifically, lambdas can now refer to:

local variables (from the scope):

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to_inch <- function(data, ...) {
  # the local variable `inch` can be used in the lambda
  inch <- 0.393701
  data %>% 
    mutate_at(vars(...), ~ . * inch)
}
iris %>% 
  as_tibble() %>% 
  to_inch(-Species)
#> # A tibble: 150 x 5
#>    Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#>           <dbl>       <dbl>        <dbl>       <dbl> <fct>  
#>  1         2.01        1.38        0.551      0.0787 setosa 
#>  2         1.93        1.18        0.551      0.0787 setosa 
#>  3         1.85        1.26        0.512      0.0787 setosa 
#>  4         1.81        1.22        0.591      0.0787 setosa 
#>  5         1.97        1.42        0.551      0.0787 setosa 
#>  6         2.13        1.54        0.669      0.157  setosa 
#>  7         1.81        1.34        0.551      0.118  setosa 
#>  8         1.97        1.34        0.591      0.0787 setosa 
#>  9         1.73        1.14        0.551      0.0787 setosa 
#> 10         1.93        1.22        0.591      0.0394 setosa 
#> # … with 140 more rows

other columns of the data (from the data mask):

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iris %>% 
  as_tibble() %>% 
  mutate_at(vars(starts_with("Sepal")), ~ . / Petal.Width)
#> # A tibble: 150 x 5
#>    Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#>           <dbl>       <dbl>        <dbl>       <dbl> <fct>  
#>  1         25.5       17.5           1.4         0.2 setosa 
#>  2         24.5       15             1.4         0.2 setosa 
#>  3         23.5       16             1.3         0.2 setosa 
#>  4         23.0       15.5           1.5         0.2 setosa 
#>  5         25         18             1.4         0.2 setosa 
#>  6         13.5        9.75          1.7         0.4 setosa 
#>  7         15.3       11.3           1.4         0.3 setosa 
#>  8         25         17             1.5         0.2 setosa 
#>  9         22         14.5           1.4         0.2 setosa 
#> 10         49         31             1.5         0.1 setosa 
#> # … with 140 more rows