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Christine Tobler

MathWorks

Last seen: 8 days ago Active since 2015

Professional Interests: numerical linear algebra, graph algorithms

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Answered
Finding number of independent pathways in a graph
I'd expect the call to rmedge is the most expensive here. You could instead add edge weights for every edge in the graph, and th...

9 days ago | 0

Answered
Feature for eigs involving just positive eigenvalues
There's no option to do so directly, since it's not a common request and there's already a lot of option names in EIGS to dig th...

23 days ago | 0

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Answered
Large sparse matrix LU decomposition
If the call to lu runs out of memory, but the call to decomposition(__, 'lu') doesn't, likely the reason is that decomposition u...

25 days ago | 0

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Answered
Facing a unbalanced matrix, such as 3*5000, why someone reduce the computational cost by svd(A*A') .
The computational complexity of svd (when using the 'econ' option, which is very necessary for matrices that are far from square...

1 month ago | 1

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Answered
Boundary 'edges' around node(s)
There is no option to do this as part of the graph plot directly. You can achieve it by turning off the node markers (set 'Marke...

1 month ago | 1

Answered
Minimum Spanning Tree - Path or Start-End
In general, you can't rely on the fact that a minimum spanning tree will just be one path. However, if you have a graph for whic...

1 month ago | 0

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Answered
how to determine efficiency centrality of a node in Matlab
There isn't an efficiency centrality implemented in MATLAB. Based on the paper I quickly read, it seems you would best compute t...

1 month ago | 0

Answered
Graph Laplacian and adjacency matrix
Take a look at pdist in the Statistics and Machine Learning toolbox. If you apply this to your matrix, and then call squareform ...

1 month ago | 0

Answered
Matrix inverse with svd
Use one of A = [ 2 4 6; 8 5 7 ; 0 3 1] [U,S,V] = svd(A); V*inv(S)*U' V*(S\U') % The formula you're using above puts the par...

2 months ago | 0

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Answered
Degree and influence of line of a node in network
The only reference for DIL I could find is a 2016 paper: Evaluating the importance of nodes in complex networks, J Liu, Q Xiong...

2 months ago | 2

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Answered
How to find all the edges connecting a specific node with other nodes?
Use outedges to find the IDs of all outgoing edges, or neighbors to find all nodes connected to by these edges.

2 months ago | 0

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Answered
Symbolic SVD for square matrix
The computation of the SVD in symbolic mathematics involves the solving of a polynomial equation of degree given by the size of ...

2 months ago | 1

Answered
Betweenness Centrality, Edge betweenness
For betweenness centrality, see centrality method of graph and digraph classes. Edge betweenness is not provided.

2 months ago | 0

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How to create random graph?
You can use s = randi(n, e, 1); t = randi(n, e, 1); G = graph(s, t, [], n); which will give you a graph with n nodes and e e...

2 months ago | 1

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Answered
Why do logical operators do not work with the eigenvalues of this matrix?
There's a small round-off error on the eigenvalue 1: >> TM = [0.1,0.2,0.7; 0.5,0.2,0.3;0.1,0.1,0.8]; [V,D] = eig(TM', 'vector'...

3 months ago | 0

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Answered
Digraph with a single constrained axis
All algorithms for graph visualization that I'm aware of will compute both x and y (and sometimes z) coordinates for the nodes. ...

3 months ago | 0

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how would i change an undirected network into a directed network on matlab?
It depends on what you want to the directed graph to look like. To replace every undirected edge with two directed edges going i...

4 months ago | 1

Answered
Both eig() and eigs() function calculate different eigenvalues depending on optional input values
The problems seen here are due to M being symmetric positive semi-definite. Such a matrix is numerically singular, which can hav...

4 months ago | 5

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Answered
Warning: Matrix is singular to working precision: What exactly generates this warning?
The warning is generated based on an estimate of the condition number (specifically, the reciprocal condition number in 1-norm, ...

4 months ago | 0

Answered
Traverse a directed graph visiting all edges at least once?
There aren't any functions for MATLAB's graph object that solve this problem. Possibly you can formulate this as an optimization...

4 months ago | 1

Answered
How to search all elements in two cell arrays?
All right, let's assume you have a graph containing both G and H stored as graph object GH, and that this graph contains the bla...

5 months ago | 0

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Answered
My Hessenberg Decomposition code is not working
Your code looks correct, try it with A = randn(10) for example - this matches the outputs of HESS quite closely. When the input ...

5 months ago | 1

Answered
Direct Solver
The direct sparse solver (\) unfortunately doesn't have methods for complex symmetric or hermitian problems, only for real symme...

5 months ago | 1

Answered
Solve large linear equations with backslash operator. Why is sparse matrix solved slower than the full matrix?
Sparse linear system solvers are usually fast for sparse matrices with specific structure of where the nonzeros are placed. For ...

5 months ago | 0

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EIGS: Why is 'smallestabs' faster than 'largestabs'?
Whether 'largestabs' or 'smallestabs' depends on the problem: 'smallestabs' needs to factorize the first input, which can make i...

5 months ago | 0

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Answered
What is the algorithm used by svd function?
We don't give information on what SVD algorithm we use, look up the LAPACK library for detailed descriptions. For practical pur...

5 months ago | 1

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Inverse of higher order matrix
Another way of looking at the equations x*Q = 0 and x e = 1 is as an equation system x * [Q e] = [0 1], which you could solve us...

5 months ago | 0

Answered
How to decompose a 4th order tensor
The value of K1111 is overwritten with the next value in every loop iteration - is this your intention, or did you maybe mean to...

6 months ago | 0

Answered
How can I find the Members of the largest component of a graph?
Use oF = F_prime.Nodes.Name(bin==m); instead of the find command to return node names instead of node numbers.

6 months ago | 1

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Answered
Projecting data points onto eigenvector space
The lambda here is a diagonal matrix, so SORT will sort each of its columns, not the eigenvalues on the diagonal among themselve...

6 months ago | 0

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