View function as flow chart

Source: R/03_0_flow_view.R, R/04_0_flow_run.R

flow_view() shows the code of a function as a flow diagram, flow_run() runs a call and draws the logical path taken by the code.

flow_view(
  x,
  prefix = NULL,
  code = TRUE,
  narrow = FALSE,
  truncate = NULL,
  nested_fun = NULL,
  swap = TRUE,
  out = NULL,
  engine = c("nomnoml", "plantuml")
)

flow_run(
  x,
  prefix = NULL,
  code = TRUE,
  narrow = FALSE,
  truncate = NULL,
  swap = TRUE,
  out = NULL,
  browse = FALSE
)

Arguments

x

a call, a function, or a path to a script

prefix

prefix to use for special comments in our code used as block headers, must start with "#", several prefixes can be provided

code

Whether to display the code in code blocks or only the header, to be more compact, if NA, the code will be displayed only if no header is defined by special comments

narrow

TRUE makes sure the diagram stays centered on one column (they'll be longer but won't shift to the right)

truncate

maximum number of characters to be printed per line

nested_fun

if not NULL, the index or name of the function definition found in x that we wish to inspect

swap

whether to change var <- if(cond) expr into if(cond) var <- expr so the diagram displays better

out

a path to save the diagram to. Special values "html", "htm", "png", "pdf", "jpg" and "jpeg" can be used to export the object to a temp file of the relevant format and open it, if a regular path is used the format will be guessed from the extension. Other special values "data" and "code" can be used for respectively retrieving the graph data as a data frame and the diagram code.

engine

either "nomnoml" (default) or "plantuml" (experimental), if the latter, arguments prefix, narrow, and code

browse

whether to debug step by step (block by block), can also be a vector of block ids, in this case browser() calls will be inserted at the start of these blocks

Value

flow_view() returns a "flow_diagram" object by default, and the output path invisibly if out is not NULL (called for side effects). flow_run() returns the output of the wrapped call.

Details

On some system the output might sometimes display the box character when using the nomnoml engine, this is due to the system not recognizing the Braille character \u2800. This character is used to circumvent a nomnoml shortcoming: lines can't start with a standard space and multiple subsequent spaces might be collapsed. To choose another character, set the option flow.indenter, for instance : options(flow.indenter = "\u00b7").

Examples

flow_view(rle)
flow_run(rle(c(1, 2, 2, 3)))
#> Run Length Encoding
#>   lengths: int [1:3] 1 2 1
#>   values : num [1:3] 1 2 3