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# Christine Tobler

### MathWorks

230 total contributions since 2015

Professional Interests: numerical linear algebra, graph algorithms

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Find border edges of the graph
The graph class doesn't have any functions based on coordinates of the points - it just knows about their connections. Use conve...

16 jours ago | 1

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QR decomposition with the output of a permutation vector
The purpose of arranging all diagonal elements in descending order is to allow splitting R into two parts if A is low-rank or cl...

17 jours ago | 0

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How to add highlighted nodes and edges of a graph to the legend?
The problem here is that legend will only provide labels for what graphics recognizes as individual objects. So in a line plot,...

23 jours ago | 1

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How to restore tensor after applied the PARAFAC model?
The three component vectors represent the 3 different dimensions here. For the one-component case (all are vectors), you can use...

environ un mois ago | 0

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Create a graph from removed edges
The graph constructor has a syntax that specifies the number of nodes of the graph: graph(s, t, [], numnodes) if you pass the ...

environ un mois ago | 0

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SVD computation using eig function
Try the formula the other way around, using U_tilde, V_tilde and A to compute D: >> U_tilde'*A*V_tilde ans = 70.0118 -0....

environ un mois ago | 0

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Using Singular value decomposition for feature extraction from images
Image compression using SVD is a pretty common example (although not the most efficient way to compress an image), here are some...

environ un mois ago | 0

Error using eig Input matrix contains NaN or Inf.
The function sossolve is part of a third-party tool, this seems to be their website: http://www.cds.caltech.edu/sostools/. It's ...

environ un mois ago | 0

How to keep track of order eigenvalue in eig or eigs?
The eigenvalues returned by EIG are not sorted in any particular order generally (for some special types of matrices (e.g. exact...

environ 2 mois ago | 1

Eigenvectors and the null function
I'm getting those two eigenvectors when I copy your code into MATLAB: >> D = [2 -1; -1 3]; eigs = eig(D); q1 = nu...

environ 2 mois ago | 0

Block-diagonalization of a matrix
There is no direct function to do this. The best is probably to write a function that does a loop through the different blocks a...

environ 2 mois ago | 0

How created a graph from unordered node list?
When a graph or digraph is specified using numbers, the assumption is that all nodes of this graph have numbers from 1:numberOfN...

environ 2 mois ago | 0

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nonsingular matrix (X) in GSVD function
These are just different but equivalent definitions: Both will result in the same C and S, the only difference is in how X is re...

environ 2 mois ago | 1

accuracy of two methods to solve eignvalues/eignvector problem
The second way is typically more accurate, because it doesn't incur additional round-off error when conputing inv(Sw) and when m...

environ 2 mois ago | 0

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Sort eigenvectors matrix.
Take a look at rsf2csf. For a block-diagonal matrix with 1-by-1 and 2-by-2 blocks, it computes a diagonal eigenvalue matrix and ...

2 mois ago | 1

Eigenvectors of an SPD matrix being saved as complex doubles
EIG does not recognize the input matrix as symmetric because it's not exactly symmetric. If you compute A = Y'*Mh*Y norm(A - A...

2 mois ago | 0

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Given a matrix A^n. Comparing normal multiplication versus Diagonalization. I expect the former to be faster but its not in my case
A^2 is just one matrix multiplication, A*A, which is much faster to do directly than the call to EIG. For larger n, A^n isn't ...

3 mois ago | 0

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how to random initialize svd function in matlab??
The linear algebra functions in MATLAB are run-to-run reproducible, meaning if you call them twice with the exact same input, yo...

3 mois ago | 1

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EigenValues of a Vibrating system
Usually for finite element problems, the stiffness matrix is passed in as the first input, and the mass matrix as the second inp...

3 mois ago | 0

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issues with Cholesky decomposition
This can happen if your matrix is close to symmetric positive semi-definite (meaning the smallest eigenvalue is around machine e...

3 mois ago | 0

The edges in a graph are always presented in the same order (sort first by source node, secondarily be target node). You can mai...

3 mois ago | 1

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Display only one eigenvalue of symbolic matrix
The eigs function is not supported for symbolic values, as it is specifically based on getting a good approximation based on an ...

3 mois ago | 0

how to do forward neighbor discovery in un-directed graph?
If I understand correctly, you want to find all nodes that are direct neighbors of n1, then all nodes that connect to n1 through...

3 mois ago | 0

Using eigs with singular matrix
The 'smallestabs' option in eigs depends on solving several linear systems with the matrix A that's being passed in. If A is sin...

4 mois ago | 0

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Change the alignment and font size of edgelabels
The edge labels provided with the plot of a graph can't be modified in terms of their alignment. However, you can add standard t...

4 mois ago | 0

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a question for defining Custom Deep Learning Layer
You can use the svd in a custom layer, however, if the SVD is used in the forward method of a custom layer, this will likely req...

4 mois ago | 0

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Control edge alpha via edge weights to visualize a dynamic network
You can set the LineStyle to be 'none' for edges that should not be displayed: >> g = digraph([3 1 2], [2 3 1], [0 0.5 1]); >>...

4 mois ago | 1

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how to create a symmetric Toeplitz matrix with bounds on eigenvalues?
You can use the MATLAB function toeplitz with one input argument (two-input returns a non-symmetric Toeplitz matrix).

4 mois ago | 0