I wish to calculate how each set of data in a tibble is different to a baseline dataset.
to plan, I wrote this R code to subtract a tibble from another of the same size:
# this works
tbl_a <- tibble(a1 = 1, a2 = 2, a3 = 3)
tbl_b <- tibble(a1 = 4, a2 = 5, a3 = 6)
tbl_a + tbl_b
# > tbl_a + tbl_b
# a1 a2 a3
# 1 5 7 9
Now I'm turning it into a set of tibbles
# compare multiple datasets to baseline of same shape
tbl_a1 <- tibble(id = "i", a1 = 1, a2 = 2, a3 = 3)
tbl_a2 <- tibble(id = "ii", a1 = 2, a2 = 3, a3 = 4)
tbl_a3 <- tibble(id = "iii", a1 = 3, a2 = 4, a3 = 5)
tbl_base <- tibble(id_base = "baseline", a1 = 4, a2 = 5, a3 = 6)
tbls <- bind_rows(tbl_a1, tbl_a2, tbl_a3)
tbls_compare <- tbls %>%
nest(set = starts_with("a")) %>%
bind_cols(tbl_base) %>%
nest(set_baseline = starts_with("a"))
# id set id_base set_baseline
# <chr> <list> <chr> <list>
# 1 i <tibble [1 × 3]> baseline <tibble [1 × 3]>
# 2 ii <tibble [1 × 3]> baseline <tibble [1 × 3]>
# 3 iii <tibble [1 × 3]> baseline <tibble [1 × 3]>
I expected to be able to perform subtraction like I could in tbl_a + tbl_b example.
However, I'm greeted with an error:
> tbls_compare %>%
+ mutate(diff_to_base = set_baseline - set)
Error in `mutate()`:
! Problem while computing `diff_to_base = set_baseline - set`.
Caused by error in `set_baseline - set`:
! non-numeric argument to binary operator
Run `rlang::last_error()` to see where the error occurred.
I tried using purrr:map but could not by myself work out a solution.
Could somebody please enlighten me?
I think you need to add rowwise, otherwise set_baseline - set will attempt to subtract a list of tibbles from a list of tibbles.
tbls_compare <- tbls %>%
nest(set = starts_with("a")) %>%
bind_cols(tbl_base) |>
nest(set_baseline = starts_with("a")) |>
rowwise() |>
mutate(diff_to_base = list(as_tibble(set_baseline - set)))
tbls_compare
# A tibble: 3 × 5
# Rowwise:
id set id_base set_baseline diff_to_base
<chr> <list> <chr> <list> <list>
1 i <tibble [1 × 3]> baseline <tibble [1 × 3]> <tibble [1 × 3]>
2 ii <tibble [1 × 3]> baseline <tibble [1 × 3]> <tibble [1 × 3]>
3 iii <tibble [1 × 3]> baseline <tibble [1 × 3]> <tibble [1 × 3]>
This is how it looks when unnested:
tbls_compare |>
unnest(cols = diff_to_base)
+ # A tibble: 3 × 7
id set id_base set_baseline a1 a2 a3
<chr> <list> <chr> <list> <dbl> <dbl> <dbl>
1 i <tibble [1 × 3]> baseline <tibble [1 × 3]> 3 3 3
2 ii <tibble [1 × 3]> baseline <tibble [1 × 3]> 2 2 2
3 iii <tibble [1 × 3]> baseline <tibble [1 × 3]> 1 1 1