# Christine Tobler

### MathWorks

Professional Interests: numerical linear algebra, graph algorithms

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**Content Feed**

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

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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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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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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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

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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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

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

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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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

| accepted

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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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

Betweenness Centrality, Edge betweenness

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

2 months ago | 0

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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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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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

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

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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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

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

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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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

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

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

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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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

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

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

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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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