[Insight-users] Radius of Gaussian?

[Neuner Markus]

Hi,

 From the documentation at 
http://www.itk.org/Doxygen/html/classitk_1_1GaussianSpatialObject.html#2b02903cc49891d37937a9bd62ec08dd

"The Radius determines the bounding box, and which points are considered 
to be inside the SpatialObject 
<http://www.itk.org/Doxygen/html/classitk_1_1SpatialObject.html>. All 
points with z-score less than the radius are in the object."

The Radius is defined through the z-score: "All points with z-score less 
than the radius are in the object."

Since your maximum is 1 and your radius is 512 this does not make sense 
because all z-scores all smaller than 1 and inside the spatial object.



motes motes wrote:
> How should the radius of the gaussian be understood? I have done this:
>
>     const unsigned int gaussianDim = 1;
>     typedef itk::GaussianSpatialObject<gaussianDim>        GaussianType;
>     typedef itk::Point<double, gaussianDim>                GaussianPoint;
>
>     const static int gaussian_radius = 512;
>     const static int gaussian_max = 1;
>     GaussianType::Pointer m_Gaussian = GaussianType::New();
>     m_Gaussian->SetMaximum(1);
>     m_Gaussian->SetRadius(512);
>
>     GaussianPoint pos;
>     for (int i=0; i<100; i++) {
>       pos[0] = -300 + i*5;
>
>       double weight = 0.0;
>       m_Gaussian->ValueAt(pos, weight);
>       std::cout << "pos = " << pos << std::endl;
>       std::cout << "weight = " << weight << std::endl;
>     }
>
> But I only get non-zero values in the range [-35, 35]:
>
> pos = [-35]
> weight = 9.87711e-267
> pos = [-30]
> weight = 3.69388e-196
> pos = [-25]
> weight = 1.91856e-136
> pos = [-20]
> weight = 1.3839e-087
> pos = [-15]
> weight = 1.38634e-049
> pos = [-10]
> weight = 1.92875e-022
> pos = [-5]
> weight = 3.72665e-006
> pos = [0]
> weight = 1
> pos = [5]
> weight = 3.72665e-006
> pos = [10]
> weight = 1.92875e-022
> pos = [15]
> weight = 1.38634e-049
> pos = [20]
> weight = 1.3839e-087
> pos = [25]
> weight = 1.91856e-136
> pos = [30]
> weight = 3.69388e-196
> pos = [35]
> weight = 9.87711e-267
> pos = [40]
>
>
> When the radius is 512 I thought that the bell curve would have
> support in the interval: [-512, 512] but it seems that the radius in
> the gaussian expresses something else.
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