[vtkusers] vtkPCAStatistics for vectors

[gregthom]

Hi Wes, thanks for pointing out the vtkPCAAnalysis filter. It looks indeed
more like what I want to achieve however I have two question.
!) How exactly do I use GetParameterisedShape method for my case ? say I
want to generate 100 new shapes. What b should I use ?
2) concerning my last post, does doing PCA on the n polydatas themselfs
differ from doing PCA on the differences (vectors) of all n-1 polydatas with
respect to one reference polydata ? 

Thank you 

G


Wes Turner wrote:
> 
> Greg,
> It looks like you are trying to calculate positional variation from a set
> of
> polydatas and synthesize other members of the family.  Look at
> vtkPCAAnalysis filter.
> 
> - Wes
> 
> On Tue, Jul 14, 2009 at 10:26 AM, gregthom <gregthom99 at yahoo.com> wrote:
> 
>>
>> Hello VTK users
>>
>> I was wondering if vtkPCAStatistics can be used for vectors instead of
>> scalars as in the example at:
>>
>> TestPCAStatistics.cxx.
>>
>> When looking at this example I see that scalar datas are added to a table
>> before adding to the pca filter, ie
>>
>> const char m0Name[] = "M0";
>>  vtkDoubleArray* dataset1Arr = vtkDoubleArray::New();
>>  dataset1Arr->SetNumberOfComponents( 1 );
>>  dataset1Arr->SetName( m0Name );
>>
>>  const char m1Name[] = "M1";
>>  vtkDoubleArray* dataset2Arr = vtkDoubleArray::New();
>>  dataset2Arr->SetNumberOfComponents( 1 );
>>  dataset2Arr->SetName( m1Name );
>>
>>  const char m2Name[] = "M2";
>>  vtkDoubleArray* dataset3Arr = vtkDoubleArray::New();
>>  dataset3Arr->SetNumberOfComponents( 1 );
>>  dataset3Arr->SetName( m2Name );
>>
>>  for ( int i = 0; i < nVals; ++ i )
>>    {
>>    int ti = i << 1;
>>    dataset1Arr->InsertNextValue( mingledData[ti] );
>>    dataset2Arr->InsertNextValue( mingledData[ti + 1] );
>>    dataset3Arr->InsertNextValue( i != 12 ? -1. : -1.001 );
>>    }
>>
>>  vtkTable* datasetTable = vtkTable::New();
>>  datasetTable->AddColumn( dataset1Arr );
>>  dataset1Arr->Delete();
>>  datasetTable->AddColumn( dataset2Arr );
>>  dataset2Arr->Delete();
>>  datasetTable->AddColumn( dataset3Arr );
>>  dataset3Arr->Delete();
>>
>>  vtkPCAStatistics* pcas = vtkPCAStatistics::New();
>>  pcas->SetInput( vtkStatisticsAlgorithm::INPUT_DATA, datasetTable );
>>  pcas->SetNormalizationSchemeByName( normScheme );
>>  pcas->SetBasisSchemeByName( "FixedBasisEnergy" );
>>  pcas->SetFixedBasisEnergy( 1. - 1e-8 );
>>
>>
>> In my case, I have 10 polydata sets and I want to do PCA on these
>> polydata
>> with the end result of producing other polydatas by taking linea
>> combinations of the eigen vectors from PCA analysis.
>>
>> Here is my approach,
>>
>>
>> 1) use one polydata as reference (P0)
>> 2) get differences between the points of P0 and each of the other 9
>> polydatas
>>    these vectors are stored as
>>    vtkDoubleArray* vectorsP0toP1array = vtkDoubleArray::New();
>>    vectorsP0toP1array->SetNumberOfComponents( 3 );
>>    vectorsP0toP1array->SetName( "vectorsP0toP1" );
>>
>>    (...)
>>
>>   vtkDoubleArray* vectorsP0toP9array = vtkDoubleArray::New();
>>    vectorsP0toP9array->SetNumberOfComponents( 3 );
>>    vectorsP0toP9array->SetName( "vectorsP0toP9" );
>>
>> 3) run PCA on the vectors
>>
>> 4) obtain a new vector by taking combinations of the PCA eigen vectors
>>    Add new vector to P0 polydata points to obtain a new polydata model
>>
>> Does anyone with experience think this will work ? Could you also please
>> help with pseudocode for 3) and 4) ? That is where I am stuck right now.
>> Will adding the vectors columns in a table as in the example work ?
>>
>> ie
>>  vtkTable* datasetTable = vtkTable::New();
>>  datasetTable->AddColumn( vectorsP0toP1array );
>>  ...
>>  datasetTable->AddColumn( vectorsP0toP9array );
>>
>> then
>>  vtkPCAStatistics* pcas = vtkPCAStatistics::New();
>>  pcas->SetInput( vtkStatisticsAlgorithm::INPUT_DATA, datasetTable ); 
>> ????
>>
>>
>>
>> Thanks for your help in advance
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> View this message in context:
>> http://www.nabble.com/vtkPCAStatistics-for-vectors-tp24480622p24480622.html
>> Sent from the VTK - Users mailing list archive at Nabble.com.
>>
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> 
> 
> 
> -- 
> Wesley D. Turner, Ph.D.
> Kitware, Inc.
> R&D Engineer
> 28 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-371-3971 x120
> 
> _______________________________________________
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> 
> Visit other Kitware open-source projects at
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> 
> Please keep messages on-topic and check the VTK FAQ at:
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> 

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