I’m trying to compose a set of partially applied functions using the purrr package. I’m noticing that I can do this with some functions but not others and I would like to know why (or what am I missing if it’s possible)?

Specifically, I can use rename, select and head (and I’ve also successfully used custom functions that I defined), but I can’t seem to use select and filter.

In the code below, if I uncomment any of those lines I get an error like object 'milespergallon' not found.

I’ve tried quoting the variables, playing in which I compose the functions, but nothing seems to work – is there a general restriction at play here?

library("purrr")
library("dplyr")

my_func = compose(
  partial(rename, "milespergallon" = mpg),         # works fine
  partial(mutate, new_col = milespergallon + cyl), # works fine
  # partial(select, milespergallon, cyl, new_col), # not sure why this one fails?
  # partial(filter, cyl > 2),                      # not sure why this one fails?
  # partial(filter, milespergallon > 20),          # not sure why this one fails?
  head,                                            # works fine
  .dir = "forward"
)

my_func(mtcars)

Without uncommenting the offending lines, I get a sensible output:

my_func(mtcars)
                  milespergallon cyl disp  hp drat    wt  qsec vs am gear carb new_col
Mazda RX4                   21.0   6  160 110 3.90 2.620 16.46  0  1    4    4    27.0
Mazda RX4 Wag               21.0   6  160 110 3.90 2.875 17.02  0  1    4    4    27.0
Datsun 710                  22.8   4  108  93 3.85 2.320 18.61  1  1    4    1    26.8
Hornet 4 Drive              21.4   6  258 110 3.08 3.215 19.44  1  0    3    1    27.4
Hornet Sportabout           18.7   8  360 175 3.15 3.440 17.02  0  0    3    2    26.7
Valiant                     18.1   6  225 105 2.76 3.460 20.22  1  0    3    1    24.1