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Christine Tobler

MathWorks

Last seen: Today |  Actif depuis 2015

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Spoken Languages:
English, French, German
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Professional Interests:
Graph and Network Algorithms, Linear Algebra, Quantum Computing, Automatic Differentiation

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Réponse apportée
What is the most computationally efficient factorization of a matrix A?
Your solution is correct. Of the factorizations you know (PA=LU, the Choleski, SVD and the QR factorization), only LU and Chole...

22 jours il y a | 1

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Improving Precision of Eigenvectors with Large Eigenvalues
The linked post is about a symmetric matrix, is this also your case? In that case (if issymmetric returns true for your matrix),...

29 jours il y a | 2

| A accepté

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Join Subgraphs into a new Graph
Here's a quick example based on a guess at how you would like to merge the graphs: G1 = graph(["A" "B" "C"], ["B" "C" "D"]); G...

environ un mois il y a | 1

| A accepté

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how to increase node/edge separation within the layer in the layered graph?
You can access the XData and YData properties of the GraphPlot object returned by plot, to move the nodes further apart. Note i...

environ 2 mois il y a | 0

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Nonorthogonal eigenvectors for general eigenvalue problem with eig() and eigs()
For simple eigenvalue problem A*x = lambda*x, the eigenvalues are real and the eigenvectors can form an orthogonal basis only if...

environ 2 mois il y a | 0

| A accepté

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Name for adjancy-to-graph algorithm?
The graph object in MATLAB uses an internal data format that is very similar to a sparse adjacency matrix, so the construction o...

environ 2 mois il y a | 0

| A accepté

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Convert an image to a graph object
From a graph theory perspective (others may have better ideas from the image processing side), I would start by making a graph o...

2 mois il y a | 0

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eigs with complex hermitian matrix, should I set opts.issym to 1?
This only matters if you pass in a function handle - if you pass in a matrix, EIGS detects if it's hermitian (real or complex) d...

2 mois il y a | 0

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Cyclebasis function for graphs not working
Yes, cyclebasis returns a fundamental cycle basis, but not necessarily the one with the shortest cycle lengths. See the document...

3 mois il y a | 1

| A accepté

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SVD computation time question
I'm not sure what causes the sharp change between iterations - I can reproduce roughly similar timings when I call svd with 3 ou...

3 mois il y a | 1

| A accepté

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What is the residual defined in eigs?
The issue is likely that eigs doesn't use the residual as you describe it: The iterative algorithm used inside of eigs when comp...

4 mois il y a | 0

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LU decomposition with 5 output arguments
As Matt says, the simplest is likely to just use decomposition object. In terms of how to solve a linear system, the doc page g...

4 mois il y a | 2

| A accepté

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Proper Installation of Tensor Toolbox
Find the path the folder that defines the class you want to use. My guess is for Tucker this will be the ttensor class (but it's...

4 mois il y a | 0

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Computing eigenvalues and eigenvectors of two symbolic matrices
eig does not support the two-input syntax for symbolic. For the call eig(B, A), if A is invertible you can instead solve eig(A\B...

4 mois il y a | 0

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Stability analysis of a time dependent Lyapunov equation
The tensorprod function doesn't do what you are looking for here, that would be kron (short for Kronecker product). It also see...

5 mois il y a | 0

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getting warning while using eigs on the matrices obtained from freefem++
If modifying the input sigma doesn't help, it's likely that for your call eigs(A, B, sigma, ...) the matrices are such that A - ...

5 mois il y a | 0

| A accepté

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Trying to construct a filtered graph using pmfg function that uses the (MATLAB-BGL) library in MacBook.
The problem seems to be with the MatlabBGL FileExchange package and specifically with the .mex files that are being provided the...

5 mois il y a | 0

| A accepté

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Can I get all of the shortest paths between all pairs of nodes in a Directed Graph in one function call
Using shortestpathtree in a loop over the starting node is the way to go. You can change the data format of the first output by ...

6 mois il y a | 1

Réponse apportée
Inconsistency between Matlab eig() function and Matlab generated C code eig() function
For code generation, the eig function doesn't have as many special-case treatments as the eig function in regular MATLAB. This m...

6 mois il y a | 2

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How to control the curvature of each edge when drawing graph object?
The curvature of the edges in this plot aren't controllable. You could turn off the edges from the graph plot, and use the plot ...

6 mois il y a | 1

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eigs function works slowly
A possible issue is that "largestreal" option works less towards the strengths of the EIGS algorithm than the default "largestab...

7 mois il y a | 0

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Why is my parfor loop running slower than a regular for loop
The problem is likely that the cost of each iteration is still too small to warrant the start-up time of the parfor loop. You c...

7 mois il y a | 0

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Quick method in solving symmetric linear equation
You can definitely use iterative methods such as pcg. The success of this usually depends on how well-conditioned your matrix is...

9 mois il y a | 1

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doc QR decomposition error
Hi, As you can see here, R is an m by n matrix and Q is an m by m matrix in the default behavior of the qr function: A = randn...

9 mois il y a | 0

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Replacing old version graphshortestpath with new shortestpath function
You can replace [ dist,path{1} ] = graphshortestpath( adjMatrix, 1, numel(newImg(:))); with [ path{1}, dist ] = shortestpath(...

9 mois il y a | 0

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Eigenvalues and Eigenvector computation on extremely bad conditioned matrices
If the matrix P has rank 120 and its size is 160, you should expect 40 eigenvalues to be Inf - this is how singularities in the ...

10 mois il y a | 0

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QR factorization of a low rank matrix
Let's start with computing a rank-2 approximation of a large matrix. In general, this would be done using the SVD, but if you kn...

10 mois il y a | 0

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Can additional information be added to the directed graph plotting node 'tooltip'?
Yes, you can do this using the dataTipTextRow function: nodeNames = {'Node A', 'Node B', 'Node C', 'Node D', 'Node E', 'Node F'...

11 mois il y a | 0

| A accepté

Réponse apportée
computational complexity of svds
There is a recent function (introduced R2020b) called svdsketch, which is using randomized linear algebra. We recommend this for...

11 mois il y a | 0

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Write Hamiltonian using kron function
For a 6-dimensional Kronecker product, you would want to take Sz = [1 0; 0 -1]; I = [1 0; 0 1]; and apply the Kronecker produ...

11 mois il y a | 0

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