This is conceptually similar to zip() in Python, or R functions
purrr::transpose() and data.table::transpose() (albeit, accepting
elements in ... instead of a single list), with one crucial difference: if
the provided objects are named, then matching is done by names, not
positions.
zip_lists(...)R lists or atomic vectors, optionally named.
A inverted list
All arguments supplied must be of the same length. If positional matching is required, then all arguments provided must be unnamed. If matching by names, then all arguments must have the same set of names, but they can be in different orders.
gradients <- list("grad_for_wt_1", "grad_for_wt_2", "grad_for_wt_3")
weights <- list("weight_1", "weight_2", "weight_3")
str(zip_lists(gradients, weights))
#> List of 3
#> $ :List of 2
#> ..$ : chr "grad_for_wt_1"
#> ..$ : chr "weight_1"
#> $ :List of 2
#> ..$ : chr "grad_for_wt_2"
#> ..$ : chr "weight_2"
#> $ :List of 2
#> ..$ : chr "grad_for_wt_3"
#> ..$ : chr "weight_3"
str(zip_lists(gradient = gradients, weight = weights))
#> List of 3
#> $ :List of 2
#> ..$ gradient: chr "grad_for_wt_1"
#> ..$ weight : chr "weight_1"
#> $ :List of 2
#> ..$ gradient: chr "grad_for_wt_2"
#> ..$ weight : chr "weight_2"
#> $ :List of 2
#> ..$ gradient: chr "grad_for_wt_3"
#> ..$ weight : chr "weight_3"
names(gradients) <- names(weights) <- paste0("layer_", 1:3)
str(zip_lists(gradients, weights[c(3, 1, 2)]))
#> List of 3
#> $ layer_1:List of 2
#> ..$ : chr "grad_for_wt_1"
#> ..$ : chr "weight_1"
#> $ layer_2:List of 2
#> ..$ : chr "grad_for_wt_2"
#> ..$ : chr "weight_2"
#> $ layer_3:List of 2
#> ..$ : chr "grad_for_wt_3"
#> ..$ : chr "weight_3"
names(gradients) <- paste0("gradient_", 1:3)
try(zip_lists(gradients, weights)) # error, names don't match
#> Error in zip_lists(gradients, weights) :
#> All names of arguments provided to `zip_lists()` must match. Call `unname()` on each argument if you want positional matching
# call unname directly for positional matching
zip_lists(unname(gradients), unname(weights))
#> [[1]]
#> [[1]][[1]]
#> [1] "grad_for_wt_1"
#>
#> [[1]][[2]]
#> [1] "weight_1"
#>
#>
#> [[2]]
#> [[2]][[1]]
#> [1] "grad_for_wt_2"
#>
#> [[2]][[2]]
#> [1] "weight_2"
#>
#>
#> [[3]]
#> [[3]][[1]]
#> [1] "grad_for_wt_3"
#>
#> [[3]][[2]]
#> [1] "weight_3"
#>
#>