Below is a reprex of my confusion. I expect when I cross a 1-row tibble with a 2-row tibble, I get a 2-row tibble. This does work with atomic column types. However, if the 2-row tibble is a list of dataframes, I don’t get a 2-row table, like expected, but a 1-row table. This does not make sense to me. Can someone explain why it is what I should expect, or if there is something I’m missing.
Cross-posted as a bug on github: https://github.com/tidyverse/tidyr/issues/1487
library(tibble)
#> Warning: package 'tibble' was built under R version 4.2.2
library(tidyr)
#> Warning: package 'tidyr' was built under R version 4.2.2
#;; This makes sense, is expected:
#;; Crossing a 1-row table with a 2-row table, I get a two row table.
(df1 <- tibble(x=1))
#> # A tibble: 1 × 1
#> x
#> <dbl>
#> 1 1
(df2 <- tibble(y=1:2))
#> # A tibble: 2 × 1
#> y
#> <int>
#> 1 1
#> 2 2
crossing(df1, df2)
#> # A tibble: 2 × 2
#> x y
#> <dbl> <int>
#> 1 1 1
#> 2 1 2
#;; This does not make sense.
#;; If the second 2-row table is a list of dataframes, I still expect a 2-row
#;; table, but I get a 1-row table.
(df3 <- tibble(y=list(tibble(y=2), tibble(y=2))))
#> # A tibble: 2 × 1
#> y
#> <list>
#> 1 <tibble [1 × 1]>
#> 2 <tibble [1 × 1]>
crossing(df1, df3)
#> # A tibble: 1 × 2
#> x y
#> <dbl> <list>
#> 1 1 <tibble [1 × 1]>
sessioninfo::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#> setting value
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#> ctype English_United States.utf8
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#> ──────────────────────────────────────────────────────────────────────────────
Created on 2023-02-26 with reprex v2.0.2
>Solution :
See ?crossing
‘crossing()’ is a wrapper around ‘expand_grid()’ that
de-duplicates and sorts its inputs
Use expand_grid instead
expand_grid(df1, df3)
# A tibble: 2 × 2
x y
<dbl> <list>
1 1 <tibble [1 × 1]>
2 1 <tibble [1 × 1]>