If one of nrow
or ncol
is not given, an attempt is
made to infer it from the length of data
and the other
parameter. If neither is given, a one-column matrix is returned.
If there are too few elements in data
to fill the matrix,
then the elements in data
are recycled. If data
has
length zero, NA
of an appropriate type is used for atomic
vectors (0
for raw vectors) and NULL
for lists.
is.matrix
returns TRUE
if x
is a vector and has a
"dim"
attribute of length 2 and FALSE
otherwise.
Note that a data.frame
is not a matrix by this
test. The function is generic: you can write methods to handle
specific classes of objects, see InternalMethods.
as.matrix
is a generic function. The method for data frames
will return a character matrix if there is only atomic columns and any
non-(numeric/logical/complex) column, applying as.vector
to factors and format
to other non-character columns.
Otherwise, the usual coercion hierarchy (logical < integer < double <
complex) will be used, e.g., all-logical data frames will be coerced
to a logical matrix, mixed logical-integer will give a integer matrix,
etc.
The default method for as.matrix
calls as.vector(x)
, and
hence e.g.coerces factors to character vectors.
When coercing a vector, it produces a one-column matrix, and
promotes the names (if any) of the vector to the rownames of the matrix.
is.matrix
is a primitive function.
The print
method for a matrix gives a rectangular layout with
dimnames or indices. For a list matrix, the entries of length not
one are printed in the form integer,7 indicating the type
and length.