Re: [eigen] inf-norm of complex-matrix columns

[Martin Senst <martin.senst@xxxxxx>]

Hi,

I think either

M.cwise().abs().colwise().maxCoeff();

or

M.cwise().abs2().colwise().maxCoeff().cwise().sqrt();

is what you want. With complex numbers, the latter version is probably faster 
since it computes fewer square roots.

Martin





Am Donnerstag 03 Juni 2010, 21:21:38 schrieb Manoj Rajagopalan:
> Hi,
> 
>    Can someone help me come up with an expression to calculate the
> infinity-norm of the columns of a matrix, treated as vectors? I want to
> calculate the modulus of the complex entries in each column, and the
> maximum within that column. Therefore, my result should be a
> vector-expression whose length is the number of rows. In the following
> case, 4.
> 
>   MatrixXcd M(5,4);
>   M.setRandom();
>   M.colwise().?????
> 
> Thanks,
> Manoj