r-lib / lobstr

Understanding complex R objects with tools similar to str()

lobstr

lobstr provides tools in the same vein as str(), which allow you to dig into the detail of an object.

Installation

Install the released version of lobstr from CRAN:

install.packages("lobstr")

You can install the development version with:

# install.packages("pak")
pak::pak("r-lib/lobstr")

Example

Abstract syntax trees

ast() draws the abstract syntax tree of R expressions:

ast(a + b + c)
#> █─`+` 
#> ├─█─`+` 
#> │ ├─a 
#> │ └─b 
#> └─c

ast(function(x = 1) {
  if (x > 0) print("Hi!")
})
#> █─`function` 
#> ├─█─x = 1 
#> ├─█─`{` 
#> │ └─█─`if` 
#> │   ├─█─`>` 
#> │   │ ├─x 
#> │   │ └─0 
#> │   └─█─print 
#> │     └─"Hi!" 
#> └─<inline srcref>

References

ref() shows hows objects can be shared across data structures by digging into the underlying __ref__erences:

x <- 1:1e6
y <- list(x, x, x)
ref(y)
#> █ [1:0x1063ac468] <list> 
#> ├─[2:0x11629ba38] <int> 
#> ├─[2:0x11629ba38] 
#> └─[2:0x11629ba38]

e <- rlang::env()
e$self <- e
ref(e)
#> █ [1:0x1068a2218] <env> 
#> └─self = [1:0x1068a2218]

A related tool is obj_size(), which computes the size of an object taking these shared references into account:

obj_size(x)
#> 680 B
obj_size(y)
#> 760 B

Call stack trees

cst() shows how frames on the call stack are connected:

f <- function(x) g(x)
g <- function(x) h(x)
h <- function(x) x
f(cst())
#>     ▆
#>  1. ├─f(cst())
#>  2. │ └─g(x)
#>  3. │   └─h(x)
#>  4. └─lobstr::cst()