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,
        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 = 99, ...)

    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 <= 2.7.x, however, using `formatC` may be slightly better.
`list.len` | numeric; maximum number of list elements to display within a level.
`...` | 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) # 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) postscript()
      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)
    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)

[Package utils version 3.1.2 Index]