R/verb-expand.R
expand.tbl_lazy.RdThis is a method for the tidyr::expand generics. It doesn't sort the
result explicitly, so the order might be different to what expand()
returns for data frames.
# S3 method for class 'tbl_lazy'
expand(data, ..., .name_repair = "check_unique")A lazy data frame backed by a database query.
Specification of columns to expand. See tidyr::expand for more details.
Treatment of problematic column names:
"minimal": No name repair or checks, beyond basic existence,
"unique": Make sure names are unique and not empty,
"check_unique": (default value), no name repair, but check they are
unique,
"universal": Make the names unique and syntactic
a function: apply custom name repair (e.g., .name_repair = make.names
for names in the style of base R).
A purrr-style anonymous function, see rlang::as_function()
This argument is passed on as repair to vctrs::vec_as_names().
See there for more details on these terms and the strategies used
to enforce them.
Another tbl_lazy. Use show_query() to see the generated
query, and use collect() to execute the query
and return data to R.
fruits <- memdb_frame(
type = c("apple", "orange", "apple", "orange", "orange", "orange"),
year = c(2010, 2010, 2012, 2010, 2010, 2012),
size = c("XS", "S", "M", "S", "S", "M"),
weights = rnorm(6)
)
# All possible combinations ---------------------------------------
fruits %>% tidyr::expand(type)
#> # Source: SQL [2 x 1]
#> # Database: sqlite 3.46.0 [:memory:]
#> type
#> <chr>
#> 1 apple
#> 2 orange
fruits %>% tidyr::expand(type, size)
#> # Source: SQL [6 x 2]
#> # Database: sqlite 3.46.0 [:memory:]
#> type size
#> <chr> <chr>
#> 1 apple XS
#> 2 apple S
#> 3 apple M
#> 4 orange XS
#> 5 orange S
#> 6 orange M
# Only combinations that already appear in the data ---------------
fruits %>% tidyr::expand(nesting(type, size))
#> # Source: SQL [4 x 2]
#> # Database: sqlite 3.46.0 [:memory:]
#> type size
#> <chr> <chr>
#> 1 apple XS
#> 2 orange S
#> 3 apple M
#> 4 orange M