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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] inf-norm of complex-matrix columns
- From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
- Date: Thu, 3 Jun 2010 16:36:56 -0400
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Oops, I didn't see the "colwise" part. I don't think lpNorm() is
supported on colwise() at the moment.
2010/6/3 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
> 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
>>
>>
>>
>>
>