Re: [eigen] inf-norm of complex-matrix columns
• To: eigen@xxxxxxxxxxxxxxxxxxx
• Subject: Re: [eigen] inf-norm of complex-matrix columns
• From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
• Date: Thu, 3 Jun 2010 16:35:39 -0400
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```Yep, and also, IIRC, we have a built-in function for that:
matrix.lpNorm<Infinity>()

Benoit

2010/6/3 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
>
>
>
>

```

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