[Insight-users] Radius of Gaussian?

[motes motes]

Hm I don't think I understand. Do you mean that z-score = radius?

And that it does not make sense to define a z-score above 1?

On this page:

http://en.wikipedia.org/wiki/Gaussian_function

various Gaussian functions are plotted. I think its clear that they
have different radius in the traditinoal sense. Eg. The red curve is
in the domain [-2, 2].



On Mon, Sep 14, 2009 at 3:15 PM, Neuner Markus <neuner.markus at gmx.net> wrote:
> Sorry for this bad sentence i accidently pressed send.
>
> A radius with 512 does not make sense because a z-score of 1 includes all
> values within +/-  the Standarddeviation.
>
>
> Neuner Markus wrote:
>>
>> 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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>>
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>