Pretty tree-like object printing

A cleaner and easier to read replacement for str for nested list-like objects

tree(
  x,
  ...,
  index_unnamed = FALSE,
  max_depth = 10L,
  max_length = 1000L,
  show_environments = TRUE,
  hide_scalar_types = TRUE,
  val_printer = crayon::blue,
  class_printer = crayon::silver,
  show_attributes = FALSE,
  remove_newlines = TRUE,
  tree_chars = box_chars()
)

Arguments

x

A tree like object (list, etc.)

...

Ignored (used to force use of names)

index_unnamed

Should children of containers without names have indices used as stand-in?

max_depth

How far down the tree structure should be printed. E.g. 1 means only direct children of the root element will be shown. Useful for very deep lists.

max_length

How many elements should be printed? This is useful in case you try and print an object with 100,000 items in it.

show_environments

Should environments be treated like normal lists and recursed into?

hide_scalar_types

Should atomic scalars be printed with type and length like vectors? E.g. x <- "a" would be shown as x<char [1]>: "a" instead of x: "a".

val_printer

Function that values get passed to before being drawn to screen. Can be used to color or generally style output.

class_printer

Same as val_printer but for the the class types of non-atomic tree elements.

show_attributes

Should attributes be printed as a child of the list or avoided?

remove_newlines

Should character strings with newlines in them have the newlines removed? Not doing so will mess up the vertical flow of the tree but may be desired for some use-cases if newline structure is important to understanding object state.

tree_chars

List of box characters used to construct tree. Needs elements $h for horizontal bar, $hd for dotted horizontal bar, $v for vertical bar, $vd for dotted vertical bar, $l for l-bend, and $j for junction (or middle child).

Value

console output of structure

Examples

x <- list(
  list(id = "a", val = 2),
  list(
    id = "b",
    val = 1,
    children = list(
      list(id = "b1", val = 2.5),
      list(
        id = "b2",
        val = 8,
        children = list(
          list(id = "b21", val = 4)
        )
      )
    )
  ),
  list(
    id = "c",
    val = 8,
    children = list(
      list(id = "c1"),
      list(id = "c2", val = 1)
    )
  )
)

# Basic usage
tree(x)
#> <list>
#> ├─<list>
#> │ ├─id: "a"
#> │ └─val: 2
#> ├─<list>
#> │ ├─id: "b"
#> │ ├─val: 1
#> │ └─children: <list>
#> │   ├─<list>
#> │   │ ├─id: "b1"
#> │   │ └─val: 2.5
#> │   └─<list>
#> │     ├─id: "b2"
#> │     ├─val: 8
#> │     └─children: <list>
#> │       └─<list>
#> │         ├─id: "b21"
#> │         └─val: 4
#> └─<list>
#>   ├─id: "c"
#>   ├─val: 8
#>   └─children: <list>
#>     ├─<list>
#>     │ └─id: "c1"
#>     └─<list>
#>       ├─id: "c2"
#>       └─val: 1

# Even cleaner output can be achieved by not printing indices
tree(x, index_unnamed = FALSE)
#> <list>
#> ├─<list>
#> │ ├─id: "a"
#> │ └─val: 2
#> ├─<list>
#> │ ├─id: "b"
#> │ ├─val: 1
#> │ └─children: <list>
#> │   ├─<list>
#> │   │ ├─id: "b1"
#> │   │ └─val: 2.5
#> │   └─<list>
#> │     ├─id: "b2"
#> │     ├─val: 8
#> │     └─children: <list>
#> │       └─<list>
#> │         ├─id: "b21"
#> │         └─val: 4
#> └─<list>
#>   ├─id: "c"
#>   ├─val: 8
#>   └─children: <list>
#>     ├─<list>
#>     │ └─id: "c1"
#>     └─<list>
#>       ├─id: "c2"
#>       └─val: 1

# Limit depth if object is potentially very large
tree(x, max_depth = 2)
#> <list>
#> ├─<list>
#> │ ├─id: "a"
#> │ └─val: 2
#> ├─<list>
#> │ ├─id: "b"
#> │ ├─val: 1
#> │ └─children: <list>...
#> └─<list>
#>   ├─id: "c"
#>   ├─val: 8
#>   └─children: <list>...

# You can customize how the values and classes are printed if desired
tree(x, val_printer = function(x) {
  paste0("_", x, "_")
})
#> <list>
#> ├─<list>
#> │ ├─id: _"a"_
#> │ └─val: _2_
#> ├─<list>
#> │ ├─id: _"b"_
#> │ ├─val: _1_
#> │ └─children: <list>
#> │   ├─<list>
#> │   │ ├─id: _"b1"_
#> │   │ └─val: _2.5_
#> │   └─<list>
#> │     ├─id: _"b2"_
#> │     ├─val: _8_
#> │     └─children: <list>
#> │       └─<list>
#> │         ├─id: _"b21"_
#> │         └─val: _4_
#> └─<list>
#>   ├─id: _"c"_
#>   ├─val: _8_
#>   └─children: <list>
#>     ├─<list>
#>     │ └─id: _"c1"_
#>     └─<list>
#>       ├─id: _"c2"_
#>       └─val: _1_