R: Compactly Display the Structure of an Arbitrary R Object

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,
    drop.deparse.attr = strO$drop.deparse.attr,
    give.head = TRUE, give.length = give.head,
    width = getOption("width"), nest.lev = 0,
    indent.str = paste(rep.int(" ", max(0, nest.lev + 1)),
                       collapse = ".."),
    comp.str = "$ ", no.list = FALSE, envir = baseenv(),
    strict.width = strO$strict.width,
    formatNum = strO$formatNum, list.len = strO$list.len,
    deparse.lines = strO$deparse.lines, ...)

strOptions(strict.width = "no", digits.d = 3, vec.len = 4,
           list.len = 99, deparse.lines = NULL,
           drop.deparse.attr = TRUE,
           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.
`drop.deparse.attr`	logical; if `TRUE` (default), `deparse(control = control)` will not have `"showAttributes"` in `control`. Used to be hard coded to `FALSE` and hence can be set via `strOptions()` for back compatibility.
`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")`, which can be abbreviated. 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 <= 2.7.x, however, using `formatC` may be slightly better.
`list.len`	numeric; maximum number of list elements to display within a level.
`deparse.lines`	numeric or `NULL` as by default, determining the `nlines` argument to `deparse()` when `object` is a `call`. When `NULL`, the `nchar.max` and `width` arguments are used to determine a smart default.
`...`	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.

Note

See the extensive annotated ‘Examples’ below.

The default method tries to “work always”, but needs to make some assumptions for the case when object has a class but no own str() method which is the typical case: There it relies on "[" and "[[" subsetting methods to be compatible with length(). When this is not the case, or when is.list(object) is TRUE, but length(object) differs from length(unclass(object)) it treats it as “irregular” and reports the contents of unclass(object) as “hidden list”.

Author(s)

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

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) # extra digits for identification of binary numbers
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) pdf()
  str(par())
  if(need.dev) graphics.off()
}
ch <- letters[1:12]; is.na(ch) <- 3:5
str(ch) # character NA's

str(list(a = "A", L = as.list(1:100)), list.len = 9)
##                                     ------------
## " .. [list output truncated] "

## Long strings,   'nchar.max'; 'strict.width' :
nchar(longch <- paste(rep(letters,100), collapse = ""))
str(longch)
str(longch, nchar.max = 52)
str(longch, strict.width = "wrap")

## Multibyte characters in strings:
## Truncation behavior (<-> correct width measurement) for "long" non-ASCII:
idx <- c(65313:65338, 65345:65350)
fwch <- intToUtf8(idx) # full width character string: each has width 2
ch <- strtrim(paste(LETTERS, collapse="._"), 64)
(ncc <- c(c.ch = nchar(ch),   w.ch = nchar(ch,   "w"),
          c.fw = nchar(fwch), w.fw = nchar(fwch, "w")))
stopifnot(unname(ncc) == c(64,64, 32, 64))
## nchar.max: 1st line needs an increase of  2  in order to see  1  (in UTF-8!):
invisible(lapply(60:66, function(N) str(fwch, nchar.max = N)))
invisible(lapply(60:66, function(N) str( ch , nchar.max = N))) # "1 is 1" here


## 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)

[Package utils version 4.4.1 Index]