diag
Diagonal Matrices
Description
Creates a diagonal matrix or extracts the diagonal elements of a matrix.
Usage
diag(x = 1, nrow, ncol, names = TRUE)
diag(x) <- value
Arguments
| x |
a matrix, vector, or one-dimensional array. Missing values (NAs) are
allowed. If you do not provide a value for x, you must specify a
value for nrow.
|
| nrow |
an integer that specifies the number of rows for the output matrix.
|
| ncol |
an integer that specifies the number of columns for the output matrix.
if you do not specify a value for ncol, the value you specified
for nrow is used. In this case, 1s are placed on the
diagonal of the result.
|
| names |
a logical value used only when x is a matrix.
If TRUE (the default) and the row and column names of input matrix are identical
(as with the return value of the var function),
then attach those names to the output vector.
If FALSE never attach names to the output vector.
|
| value |
a vector or one-dimensional array whose length is the minimum of the
number of rows and the number of columns. Missing values (NAs) are
allowed.
|
Details
By default, the matrix is square with zeros off the diagonal, but it can
be made rectangular by specifying nrow and ncol.
The diag(x) <- value form allows replacement of the values on the
diagonal of a matrix.
Value
- If x is a matrix, returns the vector of diagonal elements of
x.
- If x is a vector or one-dimensional array of length greater
than one, returns a matrix with x on its diagonal and zeroes
elsewhere.
- If x is a vector or one-dimensional array of length one, and
you do not specify values for either nrow or ncol, returns
an x by x identity matrix.
See Also
Examples
amat <- matrix(c(12,15,6,10,2,9), nrow = 2)
diag(amat) # extract diagonal elements ((1,1),(2,2),etc.)
diag(diag(amat)) # create a square matrix with
# diagonal of amat
diag(5) # 5 by 5 identity matrix
diag(nrow = 5) # same thing
diag(as.matrix(5)) # 5
x <- 1:3
diag(x, nrow = 2*length(x)) # replicate x on the diagonal of a matrix
diag(x, nrow = length(x)) # put x on the diagonal of a matrix
bmat <- matrix(1:4,2)
diag(amat) <- diag(bmat) # put diagonal of bmat into diagonal of amat