This function returns the spectral norm of a real matrix.
Usage
spectral.norm(x)
Arguments
x
a numeric matrix or vector
Details
Let {f{x}} be an m \times n real matrix. The
function computes the order n square matrixmatrix {f{A}} = {f{x'}};{f{x}}.
The R function eigen is applied to this matrix to obtain the vector
of eigenvalues {f{λ }} = ≤ft[ {egin{array}{*{20}c}
{λ _1 } & {λ _2 } & cdots & {λ _n } \
end{array}}
ight]. By construction the eigenvalues are in descending
order of value so that the largest eigenvalue is λ _1. Then
the spectral norm is ≤ft| {f{x}}
ight|_2 = √ {λ _1 }.
If {f{x}} is a vector, then {f{L}}_2 = √ {f{A}} is returned.
Value
A numeric value.
Note
If the argument x is not numeric, an error message is displayed and the function terminates.
If the argument is neither a matrix nor a vector, an error message is displayed and the
function terminates.
If the product matrix {f{x'}};{f{x}} is negative definite, an error message
displayed and the function terminates.