[Insight-users] Norm in ITK

[Lisa Dean]

Hi,



Thanks a lot Vikas, Luis.

Yes Luis, your assumption was right, the norm that I wanted was the sum of
norms of all the vectors in the array.
It worked out the way you suggested.


:)
Lisa



On 24 May 2012 06:23, Luis Ibanez <luis.ibanez at kitware.com> wrote:

> Hi Lisa,
>
>
> The only embarrassing questions
> are those that are left unasked        :-)
>
>
> At this point we don't really have an ITK
> class that encompasses the concept of
> an "Array of Vectors", although you can
> construct it with existing classes.
>
> May I presume that the norm that you want
> to compute for the Array of Vector is the
> Sum of norms of all the Vectors in the array ?
>
> If so, at this point the easy way to do this
> would be to Instantiate an Array of Vectors,
>
> and do a for loop visiting all the elements...
>
> As Array classes you could use the:
>
> typedef itk::Vectors< float, N >   VectorType;
>
> ...
>
> itk::Array< VectorType >
>
> or
>
> itk::VectorContainer<  VectorType >
>
> or simply one of the STL containers
>
> std::list< VectorType >
> std::vector< VectorType >
>
> The code could look like:
>
> typedef std::vector< VectorType >  ArrayOfVectorType;
>
> ArrayOfVectorType   array = this->GetArraySomehow();
>
> ArrayOfVectorType::const_iterator  itr = array.begin();
>
> double sum = 0.0;
> while( itr != array.end() )
>   {
>   sum += itr->GetNorm();
>   ++itr;
>   }
>
> std::cout << sum << std::endl;
>
>
> http://www.itk.org/Doxygen/html/classitk_1_1Vector.html#a0f103636ffc85fd3df1ae6c838d3e70e
>
>
>
> Depending on your definition of norm
> for an array of vectors, the code above
> may need some retouching.
>
>
>    HTH
>
>
>        Luis
>
>
> ------------------------------------------------------
> On Tue, May 22, 2012 at 2:06 AM, Lisa Dean <lisadean.leo at gmail.com> wrote:
>
>>
>>
>> Hi Users,
>>
>>
>> Forgive the embarrassingly basic question, but how do I find the squared
>> norm of an itk array of vectors?
>>
>>
>>
>> Thanks for the help
>>
>> Lisa
>>
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