head                  package:utils                  R Documentation

Return the First or Last Part of an Object

Description:

     Returns the first or last parts of a vector, matrix, table, data
     frame or function.  Since 'head()' and 'tail()' are generic
     functions, they may also have been extended to other classes.

Usage:

     head(x, ...)
     ## Default S3 method:
     head(x, n = 6, ...)
     ## S3 method for class 'data.frame':
     head(x, n = 6, ...)
     ## S3 method for class 'matrix':
     head(x, n = 6, ...)
     ## S3 method for class 'ftable':
     head(x, n = 6, ...)
     ## S3 method for class 'table':
     head(x, n = 6, ...)
     ## S3 method for class 'function':
     head(x, n = 6, ...)

     tail(x, ...)
     ## Default S3 method:
     tail(x, n = 6, ...)
     ## S3 method for class 'data.frame':
     tail(x, n = 6, ...)
     ## S3 method for class 'matrix':
     tail(x, n = 6, addrownums = TRUE, ...)
     ## S3 method for class 'ftable':
     tail(x, n = 6, addrownums = FALSE, ...)
     ## S3 method for class 'table':
     tail(x, n = 6, addrownums = TRUE, ...)
     ## S3 method for class 'function':
     tail(x, n = 6, ...)

Arguments:

       x: an object

       n: a single integer. If positive, size for the resulting object:
          number of elements for a vector (including lists), rows for a
          matrix or data frame or lines for a function. If negative,
          all but the 'n' last/first number of elements of 'x'.

addrownums: if there are no row names, create them from the row
          numbers.

     ...: arguments to be passed to or from other methods.

Details:

     For matrices, 2-dim tables and data frames, 'head()' ('tail()')
     returns the first (last) 'n' rows when 'n > 0' or all but the last
     (first) 'n' rows when 'n < 0'.  'head.matrix()' and
     'tail.matrix()' are exported.  For functions, the lines of the
     deparsed function are returned as character strings.

     If a matrix has no row names, then 'tail()' will add row names of
     the form '"[n,]"' to the result, so that it looks similar to the
     last lines of 'x' when printed.  Setting 'addrownums = FALSE'
     suppresses this behaviour.

Value:

     An object (usually) like 'x' but generally smaller.  For 'ftable'
     objects 'x', a transformed 'format(x)'.

Author(s):

     Patrick Burns, improved and corrected by R-Core. Negative argument
     added by Vincent Goulet.

Examples:

     head(letters)
     head(letters, n = -6)

     head(freeny.x, n = 10)
     head(freeny.y)

     tail(letters)
     tail(letters, n = -6)

     tail(freeny.x)
     tail(freeny.y)

     tail(library)

     head(stats::ftable(Titanic))

