Hello all,
I have a situation that I'm a little confused about. I think if I could understand the contrived situation below, then I could figure out my issue.
Essentially, when I use map(x, function(x) { !!x }) with tidyeval I get the result that I expect. When I try to use the purrr shortcut, i.e., map(x, ~ { !!. }) I get an error. I don't understand why. If anybody has insight that they care to share, I would really appreciate it!
A reprex is below:
library(tidyverse)
#> ── Attaching packages ─────────────────────────────────────────────────────────────────── tidyverse 1.2.1 ──
#> ✔ ggplot2 2.2.1 ✔ purrr 0.2.4
#> ✔ tibble 1.3.4 ✔ dplyr 0.7.4
#> ✔ tidyr 0.7.2 ✔ stringr 1.2.0
#> ✔ readr 1.1.1 ✔ forcats 0.2.0
#> ── Conflicts ────────────────────────────────────────────────────────────────────── tidyverse_conflicts() ──
#> ✖ dplyr::filter() masks stats::filter()
#> ✖ dplyr::lag() masks stats::lag()
data(mtcars)
vars <- quos(am, vs)
# This works as expected:
map_df(vars, function(x){
mtcars %>%
group_by(!!x) %>%
summarise(mean(mpg))
})
#> # A tibble: 4 x 3
#> am `mean(mpg)` vs
#> <dbl> <dbl> <dbl>
#> 1 0 17.14737 NA
#> 2 1 24.39231 NA
#> 3 NA 16.61667 0
#> 4 NA 24.55714 1
# I'm not sure why this doesn't work:
purrr::map_df(vars, ~{
mtcars %>%
group_by(!! .) %>%
summarise(mean(mpg))
})
#> Error in mutate_impl(.data, dots): Column `structure(list(mpg = c(21, 21, 22.8, 21.4, 18.7, 18.1, 14.3,
#> 24.4, 22.8, 19.2, 17.8, 16.4, 17.3, 15.2, 10.4, 10.4, 14.7, 32.4,
#> 30.4, 33.9, 21.5, 15.5, 15.2, 13.3, 19.2, 27.3, 26, 30.4, 15.8,
#> 19.7, 15, 21.4), cyl = c(6, 6, 4, 6, 8, 6, 8, 4, 4, 6, 6, 8,
#> 8, 8, 8, 8, 8, 4, 4, 4, 4, 8, 8, 8, 8, 4, 4, 4, 8, 6, 8, 4),
#> disp = c(160, 160, 108, 258, 360, 225, 360, 146.7, 140.8,
#> 167.6, 167.6, 275.8, 275.8, 275.8, 472, 460, 440, 78.7, 75.7,
#> 71.1, 120.1, 318, 304, 350, 400, 79, 120.3, 95.1, 351, 145,
#> 301, 121), hp = c(110, 110, 93, 110, 175, 105, 245, 62, 95,
#> 123, 123, 180, 180, 180, 205, 215, 230, 66, 52, 65, 97, 150,
#> 150, 245, 175, 66, 91, 113, 264, 175, 335, 109), drat = c(3.9,
#> 3.9, 3.85, 3.08, 3.15, 2.76, 3.21, 3.69, 3.92, 3.92, 3.92,
#> 3.07, 3.07, 3.07, 2.93, 3, 3.23, 4.08, 4.93, 4.22, 3.7, 2.76,
#> 3.15, 3.73, 3.08, 4.08, 4.43, 3.77, 4.22, 3.62, 3.54, 4.11
#> ), wt = c(2.62, 2.875, 2.32, 3.215, 3.44, 3.46, 3.57, 3.19,
#> 3.15, 3.44, 3.44, 4.07, 3.73, 3.78, 5.25, 5.424, 5.345, 2.2,
#> 1.615, 1.835, 2.465, 3.52, 3.435, 3.84, 3.845, 1.935, 2.14,
#> 1.513, 3.17, 2.77, 3.57, 2.78), qsec = c(16.46, 17.02, 18.61,
#> 19.44, 17.02, 20.22, 15.84, 20, 22.9, 18.3, 18.9, 17.4, 17.6,
#> 18, 17.98, 17.82, 17.42, 19.47, 18.52, 19.9, 20.01, 16.87,
#> 17.3, 15.41, 17.05, 18.9, 16.7, 16.9, 14.5, 15.5, 14.6, 18.6
#> ), vs = c(0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0,
#> 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1), am = c(1,
#> 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,
#> 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1), gear = c(4, 4, 4, 3,
#> 3, 3, 3, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 4, 4, 4, 3, 3, 3,
#> 3, 3, 4, 5, 5, 5, 5, 5, 4), carb = c(4, 4, 1, 1, 2, 1, 4,
#> 2, 2, 4, 4, 3, 3, 3, 4, 4, 4, 1, 2, 1, 1, 2, 2, 4, 2, 1,
#> 2, 2, 4, 6, 8, 2)), .Names = c("mpg", "cyl", "disp", "hp",
#> "drat", "wt", "qsec", "vs", "am", "gear", "carb"), row.names = c("Mazda RX4",
#> "Mazda RX4 Wag", "Datsun 710", "Hornet 4 Drive", "Hornet Sportabout",
#> "Valiant", "Duster 360", "Merc 240D", "Merc 230", "Merc 280",
#> "Merc 280C", "Merc 450SE", "Merc 450SL", "Merc 450SLC", "Cadillac Fleetwood",
#> "Lincoln Continental", "Chrysler Imperial", "Fiat 128", "Honda Civic",
#> "Toyota Corolla", "Toyota Corona", "Dodge Challenger", "AMC Javelin",
#> "Camaro Z28", "Pontiac Firebird", "Fiat X1-9", "Porsche 914-2",
#> "Lotus Europa", "Ford Pantera L", "Ferrari Dino", "Maserati Bora",
#> "Volvo 142E"), class = "data.frame")` must be length 32 (the number of rows) or one, not 11
