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# Christine Tobler

### MathWorks

Last seen: Today Con actividad desde 2015

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

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Respondida
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...

alrededor de 1 mes hace | 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...

alrededor de 1 mes hace | 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(...

alrededor de 2 meses hace | 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 ...

alrededor de 2 meses hace | 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...

2 meses hace | 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'...

3 meses hace | 0

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

3 meses hace | 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...

3 meses hace | 0

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Algorithm for edge connectivity of a digraph?
There is no direct method in MATLAB for computing the edge connectivity. Based on the Wikipedia page, you should be able to comp...

4 meses hace | 0

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Get coordinates of 3-D force-directed graph plot without plotting?
There isn't currently such a function available. For the example above, nearly all the time is being spent in computing the coo...

4 meses hace | 0

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Obtain eigs from matrix and partially known eigenvector
Hi Jennifer, You are right that matrix P here is a block-diagonal matrix with three blocks: [A 0 0; 0 B 0 0 0 C] And for su...

5 meses hace | 1

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finding degree and neighbor of each vertex in a subgraph H but indexing according to original graph
I think the easiest will be to build on what you started by giving the nodes in graph G names which are just the string version ...

5 meses hace | 0

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Change of parameters of Gates in quantumCircuit does not take effect
This is a bug, thank you for reporting it. As a workaround while waiting for this to be addressed, pleaseconstruct a new gate in...

5 meses hace | 1

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how to find neighbors/degree of hyperedges of a uniform hypergraph?
MATLAB doesn't support hypergraphs, but often a specific problem can be solved with just a graph or multigraph, by interpreting ...

5 meses hace | 0

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LU decomposition algorithm change
As you point out, this kind of difference in result is to be expected and is well withing expected round-off behavior. Another ...

6 meses hace | 1

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How can I plot a multilayer graph (2 layer) starting from adjacency matrices?
Here's an example of how to do this (using just some random data, since I don't have the matrices you mention above). % Choose ...

8 meses hace | 1

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How to create a random graph that is connected?
If an undirected graph is connected, it must contain at least one path that visits each node at least once. You could construct...

8 meses hace | 0

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I have a question about the distributed computing of the eig function.
EIG for distributed arrays calls into the ScaLAPACK library - the references given by ScaLAPACK documentation would be the best ...

8 meses hace | 1

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non linear eigen value problem
This isn't the standard definition of a nonlinear eigenvalue problem, where you would have only one scalar lambda. Am I underst...

8 meses hace | 0

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Issues with the normalisation of mode shapes?
eig(A, B) normalizes the eigenvectors in the B-mass norm, but only if it recognizes the input as a symmetric problem (A is symme...

10 meses hace | 0

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Proof of relation between the generalized singular values of gsvd(A,B) and gsvd(B,A)
The background for this is the 5-output form of the GSVD: [U,V,X,C,S] = gsvd(A,B) returns unitary matrices U and V, a (usually)...

10 meses hace | 0

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Update a sparse matrix efficiently
The fastest way to construct a sparse matrix will be when the inputs are sorted, first by columns and then by rows. You can veri...

11 meses hace | 1

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Given a big square matrix and some eigenvalues, how to find the corresponding eigenvectors?
I wouldn't expect a 3072-by-3072 matrix to be a problem on the machine you describe. Could you try to run the following on your ...

11 meses hace | 0

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new interface for QR decomposition in Matlab 2022a
Yes, we made this change for R2022a. I'm sorry this has caused problems for you, @Klaus Diepold, could you share how you had bee...

12 meses hace | 1

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how to find eigenvalues using the determinant ?
The determinant should only be used explicitly to solve an eigenvalue problem for symbolic calculation (for example, when you so...

alrededor de 1 año hace | 2

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GUI crashes when using eigs with a nonzero shift on a large generalised eigenvalue problem.
Ideally this shouldn't crash, but produce an out-of-memory error. However, for example on Linux there is the "out-of-memory kill...

alrededor de 1 año hace | 0

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GPU speed up for pcg() is disappointing
It looks like you can simply replace your current call to pcg with x = pcg(A, b, tol, 5000, @(y) L\y, @(y)L'\y); as the error ...

alrededor de 1 año hace | 0

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What is matlab doing under the hood when I solve this generalized eigenvalue problem?
You can use the Display option to get some more information on what's going on inside of eigs. load matrices.mat [V,D] = eigs(...

alrededor de 1 año hace | 1