[pdal] Eigenvalues for .las Data

[Joseph S Faraguna]

Great, thanks.

On Mon, Jul 8, 2019, 12:56 PM Bradley Chambers <brad.chambers at gmail.com>
wrote:

> It is the covariance of the XYZ coordinates alone.
>
> On Mon, Jul 8, 2019 at 12:47 PM Joseph S Faraguna <faraguna at mit.edu>
> wrote:
>
>> Hi everyone,
>>
>> I am wondering what matrix is passed into Eigen's SelfAdjointEigenSolver
>> <https://eigen.tuxfamily.org/dox/classEigen_1_1SelfAdjointEigenSolver.html>
>> when filters.eigenvalues is called on a .las file. The
>> filters.eigenvalues documentation states that the decomposition is
>> performed for each point with knn nearest neighbors, but to my
>> understanding decompositions can only be performed on square matrices. I
>> was originally imagining a matrix of points like
>>
>> [x0 x1 x2 x3 ... xknn]
>>
>> ]y0 y1 y2 y3 ... yknn]
>>
>> [z0 z1 z2 z3 ... zknn]
>>
>> but this would definitely not be square. Is it a covariance matrix for
>> all points, kind of analagous to PCA?
>>
>> Best,
>>
>> Joe Faraguna
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>
>
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