matrix {base}  R Documentation 
matrix
creates a matrix from the given set of values.
as.matrix
attempts to turn its argument into a matrix.
is.matrix
tests if its argument is a (strict) matrix.
matrix(data = NA, nrow = 1, ncol = 1, byrow = FALSE, dimnames = NULL) as.matrix(x, ...) ## S3 method for class 'data.frame' as.matrix(x, rownames.force = NA, ...) is.matrix(x)
data 
an optional data vector (including a list or

nrow 
the desired number of rows. 
ncol 
the desired number of columns. 
byrow 
logical. If 
dimnames 
A 
x 
an R object. 
... 
additional arguments to be passed to or from methods. 
rownames.force 
logical indicating if the resulting matrix
should have character (rather than 
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 onecolumn 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 noncharacter columns.
Otherwise, the usual coercion hierarchy (logical < integer < double <
complex) will be used, e.g., alllogical data frames will be coerced
to a logical matrix, mixed logicalinteger 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 onecolumn 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.
If you just want to convert a vector to a matrix, something like
dim(x) < c(nx, ny) dimnames(x) < list(row_names, col_names)
will avoid duplicating x
.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
data.matrix
, which attempts to convert to a numeric
matrix.
A matrix is the special case of a twodimensional array
.
is.matrix(as.matrix(1:10)) !is.matrix(warpbreaks) # data.frame, NOT matrix! warpbreaks[1:10,] as.matrix(warpbreaks[1:10,]) # using as.matrix.data.frame(.) method ## Example of setting row and column names mdat < matrix(c(1,2,3, 11,12,13), nrow = 2, ncol = 3, byrow = TRUE, dimnames = list(c("row1", "row2"), c("C.1", "C.2", "C.3"))) mdat