isSymmetric {base} | R Documentation |
Generic function to test if object
is symmetric or not.
Currently only a matrix method is implemented, where a
complex
matrix Z
must be “Hermitian” for
isSymmetric(Z)
to be true.
isSymmetric(object, ...)
## S3 method for class 'matrix'
isSymmetric(object, tol = 100 * .Machine$double.eps,
tol1 = 8 * tol, ...)
object |
any R object; a |
tol |
numeric scalar >= 0. Smaller differences are not
considered, see |
tol1 |
numeric scalar >= 0. |
... |
further arguments passed to methods; the matrix method
passes these to |
The matrix
method is used inside eigen
by
default to test symmetry of matrices up to rounding error, using
all.equal
. It might not be appropriate in all
situations.
Note that a matrix m
is only symmetric if its rownames
and
colnames
are identical. Consider using unname(m)
.
logical indicating if object
is symmetric or not.
eigen
which calls isSymmetric
when its
symmetric
argument is missing.
isSymmetric(D3 <- diag(3)) # -> TRUE
D3[2, 1] <- 1e-100
D3
isSymmetric(D3) # TRUE
isSymmetric(D3, tol = 0) # FALSE for zero-tolerance
## Complex Matrices - Hermitian or not
Z <- sqrt(matrix(-1:2 + 0i, 2)); Z <- t(Conj(Z)) %*% Z
Z
isSymmetric(Z) # TRUE
isSymmetric(Z + 1) # TRUE
isSymmetric(Z + 1i) # FALSE -- a Hermitian matrix has a *real* diagonal
colnames(D3) <- c("X", "Y", "Z")
isSymmetric(D3) # FALSE (as row and column names differ)
isSymmetric(D3, check.attributes=FALSE) # TRUE (as names are not checked)