Convert a Nested List to Tree Data

Usage

list_stats(x, max_depth = NULL)

Arguments

x

A nested list to traverse.

Lists are traversed recursively. Non-list objects are treated as leaves. Data frames are not traversed and are treated as leaf values.

max_depth

Maximum depth to display.

A single non-negative integer or NULL. If NULL, the full nested structure is displayed. If supplied, only nodes with depth less than or equal to max_depth are included. This value is passed directly to list_stats().

Value

A list with two data frames:

nodes: one row per visited node, with columns:
- id: integer node id assigned in traversal order;
- parent: integer id of the parent node, or NA for the root;
- name: node name, using positional indices for unnamed elements;
- type: object type. Data frames are labelled "data.frame", lists are labelled "list", and other objects use base::typeof();
- path: dot-separated path from "root" to the node;
- depth: integer depth, where the root has depth 0;
- is_leaf: logical indicating whether the node is not traversed further.
edges: one row per parent-child relationship, with columns:
- from: parent node id;
- to: child node id.

If no nodes or edges are produced, empty data frames with the same column structure are returned.

Examples

x <- list(
  a = 1,
  b = list(
    x = 2,
    y = list(i = 3, j = 4)
  ),
  unnamed = list(5, z = 6),
  df = data.frame(v = 1:2)
)

stats <- list_stats(x)

stats$nodes
#>    id parent    name       type           path depth is_leaf
#> 1   1     NA    root       list           root     0   FALSE
#> 2   2      1       a     double         root.a     1    TRUE
#> 3   3      1       b       list         root.b     1   FALSE
#> 4   4      3       x     double       root.b.x     2    TRUE
#> 5   5      3       y       list       root.b.y     2   FALSE
#> 6   6      5       i     double     root.b.y.i     3    TRUE
#> 7   7      5       j     double     root.b.y.j     3    TRUE
#> 8   8      1 unnamed       list   root.unnamed     1   FALSE
#> 9   9      8       1     double root.unnamed.1     2    TRUE
#> 10 10      8       z     double root.unnamed.z     2    TRUE
#> 11 11      1      df data.frame        root.df     1    TRUE
stats$edges
#>    from to
#> 1     1  2
#> 2     1  3
#> 3     3  4
#> 4     3  5
#> 5     5  6
#> 6     5  7
#> 7     1  8
#> 8     8  9
#> 9     8 10
#> 10    1 11

# Limit traversal depth
list_stats(x, max_depth = 1)
#> $nodes
#>   id parent    name       type         path depth is_leaf
#> 1  1     NA    root       list         root     0   FALSE
#> 2  2      1       a     double       root.a     1    TRUE
#> 3  3      1       b       list       root.b     1   FALSE
#> 4  4      1 unnamed       list root.unnamed     1   FALSE
#> 5  5      1      df data.frame      root.df     1    TRUE
#> 
#> $edges
#>   from to
#> 1    1  2
#> 2    1  3
#> 3    1  4
#> 4    1  5
#> 

# Unnamed elements use their position as the node name
list_stats(list(10, a = list(20)))$nodes
#>   id parent name   type     path depth is_leaf
#> 1  1     NA root   list     root     0   FALSE
#> 2  2      1    1 double   root.1     1    TRUE
#> 3  3      1    a   list   root.a     1   FALSE
#> 4  4      3    1 double root.a.1     2    TRUE

Convert a Nested List to Tree Data

Usage

Arguments

Value

See also

Examples