Create a full Cartesian product of declared levels

Produces all combinations of the specified levels (equivalent to SQL CROSS JOIN). Use link_levels to sample N rows from the product with an optional correlation structure.

Usage

cross_levels(.by, ...)

Arguments

.by: Character vector of level names to cross (must have been created by add_level or declare_level in the same fabricate call).
...: Additional column expressions evaluated after crossing.

Value

A fabricatr_level object, meaningful only as a named argument to fabricate. It contributes one row per combination of the levels named in .by, so the frame has as many rows as their sizes multiplied together, carrying every column of those levels plus an ID column of its own. The first level in .by varies fastest.

Examples

fabricate(
  countries = declare_level(N = 10, gdp = runif(N, 1, 10)),
  years     = declare_level(N = 5, shock = runif(N, 0, 1)),
  obs       = cross_levels(.by = c("countries", "years"), Y = gdp + shock)
)
#> # A tibble: 50 × 6
#>    countries   gdp years shock obs       Y
#>    <chr>     <dbl> <chr> <dbl> <chr> <dbl>
#>  1 01         8.88 1     0.546 01     9.42
#>  2 02         3.64 1     0.546 02     4.19
#>  3 03         3.02 1     0.546 03     3.57
#>  4 04         7.22 1     0.546 04     7.76
#>  5 05         3.81 1     0.546 05     4.36
#>  6 06         5.35 1     0.546 06     5.90
#>  7 07         2.10 1     0.546 07     2.64
#>  8 08         7.21 1     0.546 08     7.76
#>  9 09         3.84 1     0.546 09     4.39
#> 10 10         8.35 1     0.546 10     8.89
#> # ℹ 40 more rows