Sparse metrix higher value as input value

I want to create a sparse matrix and then sort it. But after initialisation, the highest value in the sparse matrix is higher than the highest input value.

load('inputs.mat');
vertexFaceConnectivity=sparse(F(:),ind,ind,numVertices,numFaces);
vertexFaceConnectivity=sort(vertexFaceConnectivity,2,'descend');
max(vertexFaceConnectivity(:)) % 3658

ans = 
   (1,1)           3658

Answer 1

[Harald]

Hi Frederic,

you may not be using sparse the way you intend. In this syntax, the third input is the values of the sparse matrix. Perhaps, you wanted something more like

vertexFaceConnectivity=sparse(ind,ind,F(:),numVertices,numFaces);

Since ind repeats values, that however would mean that you are setting the same values repeatedly - is that intended?. sparse then sums those values, as you can see in this mini-example:

ind = [1 2 3 1 2 3];
F = 1:6;
sparse(ind, ind, F)

ans = 
   (1,1)        5
   (2,2)        7
   (3,3)        9

If I had to guess, I would think that you intended to create a tri-diagonal matrix? I would use spdiags for that.

Best wishes,

Harald