Matrix (version 0.999375-2)

forceSymmetric: Force a Matrix to 'symmetricMatrix' Without Symmetry Checks

Description

Force x (inheriting from Matrix class) to symmetricMatrix, without a symmetry check (which is applied for all as(x, "symmetricMatrix") alikes).

Usage

forceSymmetric(x, uplo)

Arguments

x

a (classed) square matrix.

uplo

optional string, "U" or "L". The default is "U" unless x already has a uplo slot (i.e., when it is symmetricMatrix, or

Value

• a square matrix inheriting from class symmetricMatrix.

See Also

symmpart for the symmetric part, or the coercions as(x, ).

Examples

## Hilbert matrix
 i <- 1:6
 h6 <- 1/outer(i - 1L, i, "+")
 sd <- sqrt(diag(h6))
 hh <- t(h6/sd)/sd # theoretically symmetric
 isSymmetric(hh, tol=0) # FALSE; hence
 try( as(hh, "symmetricMatrix") ) # fails, but this works fine:
 H6 <- forceSymmetric(hh)

 ## result can be pretty surprising:
 (M <- Matrix(1:36, 6))
 forceSymmetric(M) # symmetric, hence very different in lower triangle
 (tm <- tril(M))
 forceSymmetric(tm)