Use a function name that's a string in map loop?

Question

Some code:

mymtcars <- mtcars %>% head %>% rownames_to_column('model') %>% group_by(vs) %>% nest
mymtcars
     vs data             
  <dbl> <list>           
1     0 <tibble [3 × 11]>
2     1 <tibble [3 × 11]>

I can fit a linear model on this list column df like so:

mymtcars %>% 
+   mutate(mod = map(.x = data, ~ lm(.x$mpg ~ .x$cyl)))
# A tibble: 2 x 3
# Groups:   vs [2]
     vs data              mod   
  <dbl> <list>            <list>
1     0 <tibble [3 × 11]> <lm>  
2     1 <tibble [3 × 11]> <lm>  

What if my function name is a field?

mymtcars2 <- mtcars %>% head %>% rownames_to_column('model') %>% group_by(vs) %>% nest %>% crossing(func = c('lm'))
> mymtcars2
# A tibble: 2 x 3
     vs data              func 
  <dbl> <list>            <chr>
1     0 <tibble [3 × 11]> lm   
2     1 <tibble [3 × 11]> lm

I gave it a try with:

mymtcars2 %>% 
+   mutate(mod = map2(.x = data, .y = func, ~ .y(.x$mpg ~ .x$cyl)))
Error: Problem with `mutate()` input `mod`.
x could not find function ".y"
ℹ Input `mod` is `map2(.x = data, .y = func, ~.y(.x$mpg ~ .x$cyl))`.

How can I pass the function to call in map and then call it in the above block?

Answer 1

May be using match.fun inside map2 like below:

   models <-  mymtcars2 %>% 
       mutate(mod = map2(.x = data, .y = func, ~ match.fun(.y)(.x$mpg ~ .x$cyl)))

Output:

[[1]]

Call:
match.fun(.y)(formula = .x$mpg ~ .x$cyl)

Coefficients:
(Intercept)       .x$cyl  
  36.926733    -2.728218  


[[2]]

Call:
match.fun(.y)(formula = .x$mpg ~ .x$cyl)

Coefficients:
(Intercept)       .x$cyl  
    41.9400      -3.8025  

Answer 2

I also found that I can use get:

mymtcars2 %>% 
  mutate(mod = map2(.x = data, .y = func, ~ get(.y)(.x$mpg ~ .x$cyl)))

Am unsure of when to use one over the other.