str {utils}

R Documentation

Compactly Display the Structure of an Arbitrary R Object

Description

Compactly display the internal structure of an R object, a diagnostic function and an alternative to summary (and to some extent, dput). Ideally, only one line for each ‘basic’ structure is displayed. It is especially well suited to compactly display the (abbreviated) contents of (possibly nested) lists. The idea is to give reasonable output for any R object. It calls args for (non-primitive) function objects.

strOptions() is a convenience function for setting options(str = .), see the examples.

Usage

str(object, ...)

## S3 method for class 'data.frame'
str(object, ...)

## Default S3 method:
str(object, max.level = NA,
    vec.len  = strO$vec.len, digits.d = strO$digits.d,
    nchar.max = 128, give.attr = TRUE,
    give.head = TRUE, give.length = give.head,
    width = getOption("width"), nest.lev = 0,
    indent.str = paste(rep.int(" ", max(0, nest.lev + 1)),
                       collapse = ".."),
    comp.str="$ ", no.list = FALSE, envir = baseenv(),
    strict.width = strO$strict.width,
    formatNum = strO$formatNum, ...)

strOptions(strict.width = "no", digits.d = 3, vec.len = 4,
           formatNum = function(x, ...)
                       format(x, trim=TRUE, drop0trailing=TRUE, ...))

Arguments

object	any R object about which you want to have some information.
max.level	maximal level of nesting which is applied for displaying nested structures, e.g., a list containing sub lists. Default NA: Display all nesting levels.
vec.len	numeric (>= 0) indicating how many ‘first few’ elements are displayed of each vector. The number is multiplied by different factors (from .5 to 3) depending on the kind of vector. Defaults to the vec.len component of option "str" (see options) which defaults to 4.
digits.d	number of digits for numerical components (as for print). Defaults to the digits.d component of option "str" which defaults to 3.
nchar.max	maximal number of characters to show for character strings. Longer strings are truncated, see longch example below.
give.attr	logical; if TRUE (default), show attributes as sub structures.
give.length	logical; if TRUE (default), indicate length (as [1:...]).
give.head	logical; if TRUE (default), give (possibly abbreviated) mode/class and length (as <type>[1:...]).
width	the page width to be used. The default is the currently active options("width"); note that this has only a weak effect, unless strict.width is not "no".
nest.lev	current nesting level in the recursive calls to str.
indent.str	the indentation string to use.
comp.str	string to be used for separating list components.
no.list	logical; if true, no ‘list of ...’ nor the class are printed.
envir	the environment to be used for promise (see delayedAssign) objects only.
strict.width	string indicating if the width argument's specification should be followed strictly, one of the values c("no", "cut", "wrap"). Defaults to the strict.width component of option "str" (see options) which defaults to "no" for back compatibility reasons; "wrap" uses strwrap(*, width=width) whereas "cut" cuts directly to width. Note that a small vec.length may be better than setting strict.width = "wrap".
formatNum	a function such as format for formatting numeric vectors. It defaults to the formatNum component of option "str", see “Usage” of strOptions() above, which is almost back compatible to R version \le 2.7.x, however, using formatC may be slightly better.
...	potential further arguments (required for Method/Generic reasons).

Value

str does not return anything, for efficiency reasons. The obvious side effect is output to the terminal.

Author(s)

Martin Maechler maechler@stat.math.ethz.ch since 1990.

See Also

ls.str for listing objects with their structure; summary, args.

Examples

require(stats); require(grDevices); require(graphics)
## The following examples show some of 'str' capabilities
str(1:12)
str(ls)
str(args) #- more useful than  args(args) !
str(freeny)
str(str)
str(.Machine, digits.d = 20)
str( lsfit(1:9,1:9))
str( lsfit(1:9,1:9), max.level = 1)
str( lsfit(1:9,1:9), width = 60, strict.width = "cut")
str( lsfit(1:9,1:9), width = 60, strict.width = "wrap")
op <- options(); str(op) # save first;
                         # otherwise internal options() is used.
need.dev <-
  !exists(".Device") || is.null(.Device) || .Device == "null device"
{ if(need.dev) postscript()
  str(par())
  if(need.dev) graphics.off()
}
ch <- letters[1:12]; is.na(ch) <- 3:5
str(ch) # character NA's

nchar(longch <- paste(rep(letters,100), collapse=""))
str(longch)
str(longch, nchar.max = 52)

str(longch, strict.width = "wrap")

## Settings for narrow transcript :
op <- options(width = 60,
              str = strOptions(strict.width = "wrap"))
str(lsfit(1:9,1:9))
str(options())
## reset to previous:
options(op)



str(quote( { A+B; list(C,D) } ))



## S4 classes :
require(stats4)
x <- 0:10; y <- c(26, 17, 13, 12, 20, 5, 9, 8, 5, 4, 8)
ll <- function(ymax=15, xh=6)
      -sum(dpois(y, lambda=ymax/(1+x/xh), log=TRUE))
fit <- mle(ll)
str(fit)

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