cbind                  package:base                  R Documentation

Combine R Objects by Rows or Columns

Description:

     Take a sequence of vector, matrix or data frames arguments and
     combine by _c_olumns or _r_ows, respectively.  These are generic
     functions with methods for other R classes.

Usage:

     cbind(..., deparse.level = 1)
     rbind(..., deparse.level = 1)

Arguments:

     ...: vectors or matrices.  These can be given as named arguments. 
          Other R objects will be coerced as appropriate: see section
          Details and Value.  (For the '"data.frame"' method of 'cbind'
          these can be further arguments to 'data.frame' such as
          'stringsAsFactors' and 'check.names'.)

deparse.level: integer controlling the construction of labels in the
          case of "non-matrix-like" arguments (i.e., for the default
          method):
           'deparse.level = 0' constructs no labels; the default,
          'deparse.level = 1 or 2' constructs labels from the argument
          names, see the 'Value' section below.

Details:

     The functions 'cbind' and 'rbind' are S3 generic, with methods for
     data frames.  The data frame method will be used if at least one
     argument is a data frame and the rest are vectors or matrices. 
     There can be other methods; in particular, there is one for time
     series objects.

     In the default method, all the vectors/matrices must be atomic
     (see 'vector') or lists.  Expressions are not allowed. Language
     objects (such as formulae and calls) and pairlists will be coerced
     to lists: other objects (such as names and external pointers) will
     be included as elements in a list result.

     If there are several matrix arguments, they must all have the same
     number of columns (or rows) and this will be the number of columns
     (or rows) of the result.  If all the arguments are vectors, the
     number of columns (rows) in the result is equal to the length of
     the longest vector.  Values in shorter arguments are recycled to
     achieve this length (with a 'warning' if they are recycled only
     _fractionally_).

     When the arguments consist of a mix of matrices and vectors the
     number of columns (rows) of the result is determined by the number
     of columns (rows) of the matrix arguments.  Any vectors have their
     values recycled or subsetted to achieve this length.

     For 'cbind' ('rbind'), vectors of zero length (including 'NULL')
     are ignored unless the result would have zero rows (columns), for
     S compatibility. (Zero-extent matrices do not occur in S3 and are
     not ignored in R.)

     The 'rbind' data frame method takes the classes of the columns
     from the first data frame, and matches columns by name (rather
     than by position).  Factors have their levels expanded as
     necessary (in the order of the levels of the levelsets of the
     factors encountered) and the result is an ordered factor if and
     only if all the components were ordered factors.  (The last point
     differs from S-PLUS.)

Value:

     A matrix or data frame combining the '...' arguments column-wise
     or row-wise.  (Exception: if all the inputs are 'NULL', the value
     is 'NULL'.)

     For 'cbind' ('rbind') the column (row) names are taken from the
     'colnames' ('rownames') of the arguments if these are matrix-like.
      Otherwise from the names of the arguments or where those are not
     supplied and 'deparse.level > 0', by deparsing the expressions
     given, for 'deparse.level = 1' only if that gives a sensible name
     (a 'symbol', see 'is.symbol').

     The names will depend on whether data frames are included: see the
     examples.

     If a matrix is created, it will be a list if any of the inputs is
     not NULL nor an atomic vector.   Otherwise its type is determined
     from the highest type of the inputs in the hierarchy NULL < raw <
     logical < integer < real < complex < character < list.

Note:

     The method dispatching is _not_ done via 'UseMethod()', but by
     C-internal dispatching. Therefore, there is no need for, e.g.,
     'rbind.default'.

     The dispatch algorithm is described in the source file
     ('.../src/main/bind.c') as

        1.  For each argument we get the list of possible class
           memberships from the class attribute.

        2.  We inspect each class in turn to see if there is an an
           applicable method.

        3.  If we find an applicable method we make sure that it is
           identical to any method determined for prior arguments. If
           it is identical, we proceed, otherwise we immediately drop
           through to the default code.

     If you want to combine other objects with data frames, it may be
     necessary to coerce them to data frames first.  (Note that this
     algorithm can result in calling the data frame method if the
     arguments are all either data frames or vectors, and this will
     result in the coercion of character vectors to factors.)

References:

     Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
     Language_. Wadsworth & Brooks/Cole.

See Also:

     'c' to combine vectors (and lists) as vectors, 'data.frame' to
     combine vectors and matrices as a data frame.

Examples:

     m <- cbind(1, 1:7) # the '1' (= shorter vector) is recycled
     m
     m <- cbind(m, 8:14)[, c(1, 3, 2)] # insert a column
     m
     cbind(1:7, diag(3))# vector is subset -> warning

     cbind(0, rbind(1, 1:3))
     cbind(I=0, X=rbind(a=1, b=1:3))  # use some names
     xx <- data.frame(I=rep(0,2))
     cbind(xx, X=rbind(a=1, b=1:3))   # named differently

     cbind(0, matrix(1, nrow=0, ncol=4))#> Warning (making sense)
     dim(cbind(0, matrix(1, nrow=2, ncol=0)))#-> 2 x 1

     ## deparse.level
     dd <- 10
     rbind(1:4, c=2, "a++" = 10, dd, deparse.level=0)# middle 2 rownames
     rbind(1:4, c=2, "a++" = 10, dd, deparse.level=1)# 3 rownames (default)
     rbind(1:4, c=2, "a++" = 10, dd, deparse.level=2)# 4 rownames

