Syntax of norm - What does 'Fro' mean?

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1

In the manual, I found the following for the command “norm”:

⋆ norm: norms for real and complex vectors and matrices. Convex. The oneargument
version norm(x) computes the 2-norm for vectors and induced 2-norm
(maximum singular value) for matrices. The two-argument version norm(x,p)
is supported as follows:
– For vectors, all p ≥ 1 are accepted, but see Appendix D.2 for more details
about how cvx handles values other than 1, 2, and Inf.
– For matrices, p must be 1, 2, Inf, or ’Fro’.

So my question is - what does 'Fro" mean?

Many thanks!
Frank

2

norm(X,‘fro’) is the Frobenius norm, that is sqrt(sum(diag(X’*X)))
which also equals norm(X(:)) = norm(X(:),2) , i.e., the square root of the sum of all squared elements in the matrix…

Note that as stated in the online help, you have to enter it as ‘fro’, not '‘Fro’…

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3

Thank you so much for your prompt reply, Mark!