Constructing a 3D matrix out of single column coordinate data with a corresponding value
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Hi,
I need to analyze a 3d velocity field from tecplot. I could transfer the data into a 4 column matrix consisting of 6644672 rows. The first three columns represent that XYZ respectively, and the fourth column is the velocity data at that coordinate.
Since I want to filter this field in the future, I for now need to construct a 3d Matrix out of this imported data. It is important that no coordinates get lost, that the velocity value stays at the right coordinate and that the coordinates are oriented in the right way to eachother.
The challenging thing for me was that the coordinates in the 4 column matrix are not ordered in some logical way.
Can someone help me?
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Catalytic
2024년 3월 28일
What would the voxels of the 3D matrix contain, and how would those contents be related to the imported data?
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Matt J
2024년 3월 28일
편집: Matt J
2024년 3월 28일
Let's call your Nx4 matrix XYZV.
xyzv=num2cell(sortrows(XYZV,[3,2,1]) ,1);
[I,J,K,V] =deal(xyzv{:});
I=findgroups(I);
J=findgroups(J);
K=findgroups(K);
matrix3D=accumarray([I,J,K], V); %the result
댓글 수: 3
Matt J
2024년 3월 29일
It means your (x,y,z) data do not sweep over a cube exactly. You could try the modification below, which allows the (x,y,z) to deviate from the nodes of a cube with a tolerance, but I don't/can't know what the appropriate TOL for your data would be.
TOL=1e-4; %example
I=findgroupstol(I,TOL);
J=findgroupstol(J,TOL);
K=findgroupstol(K,TOL);
function G=findgroupstol(U,tol)
[~,~,G]=uniquetol(U,tol);
end
추가 답변 (1개)
Matt J
2024년 3월 28일
편집: Matt J
2024년 3월 28일
If you are trying to query velocity values at arbitrary 3D locations, do not use a 3D array. Instead, use scatteredInterpolant or griddata.
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