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.
Usage
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)
Arguments
an optional data vector (including a list or
expression
vector). Non-atomic classed
R
objects are
coerced by
as.vector
and all attributes discarded.
the desired number of rows.
the desired number of columns.
byrow
logical. If
FALSE
(the default) the matrix is
filled by columns, otherwise the matrix is filled by rows.
dimnames
A
dimnames
attribute for the matrix:
NULL
or a
list
of length 2 giving the row and column
names respectively. An empty list is treated as
NULL
, and a
list of length one as row names. The list can be named, and the
list names will be used as names for the dimensions.
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
NULL
)
rownames
. The default,
NA
, uses
NULL
rownames if the data frame has ‘automatic’ row.names or for a
zero-row data frame.
Details
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,
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.
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 and preserve
class(x) which may be useful, e.g.,
for Date objects.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
The New S Language.
Wadsworth & Brooks/Cole.
See Also
data.matrix, which attempts to convert to a numeric
matrix.
A matrix is the special case of a two-dimensional array.
Since R 4.0.0, inherits(m, "array") is true for a
matrix m.
Examples
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")))
