# Christine Tobler

### MathWorks

Professional Interests: numerical linear algebra, graph algorithms

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**Content Feed**

Why does mldivide solve equations so fast that FORTRAN can't compare it？

MATLAB's mldivide uses multithreading. It doesn't use the GPU unless you have the Parallel Computing Toolbox and are using the g...

environ 14 heures ago | 0

How to highlight single edges in an undirected graph?

Do you still want the multiple edges to be displayed? If not, you can use the simplify command to reduce all multiple edges to j...

17 jours ago | 1

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Unable to find out left eigen vectors of symbolic matrix

The left eigenvectors are still expressed as right eigenvectors of M', meaning they satisfy a slightly different equation: syms...

21 jours ago | 0

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Program to find connected and non-isomorphic graphs

In the last loop, you are checking if adj is isomorphic to any previous graph. If there is one graph that adj is not isomorphic ...

24 jours ago | 0

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How can I invert a big matrix e.g. 1000-by-1000

When running inv on this matrix, there's a warning: >> M = inv(current_Fit_Mat); Warning: Matrix is close to singular or badly...

2 mois ago | 0

Add an automatic TOC to an .mlx

You can go the "Insert" tab (just to the right of where it says "Live Editor" on top of the MATLAB window) and there's a button ...

2 mois ago | 0

How to get a Table Contents in Live Script .mlx export to HTLM

You can go the "Insert" tab (just to the right of where it says "Live Editor" on top of the MATLAB window) and there's a button ...

2 mois ago | 0

How is SVDS execution time related to the target rank?

So the goal of svds is usually to compute a requested rank that is much smaller than either size of the input matrix. A search s...

2 mois ago | 0

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How to solve eigs/checkInputs issue in EOF analysis?

The error here is happening because R eof>mycaleof is an empty matrix, and eof is trying to compute an eigenvalue of it. Looking...

2 mois ago | 0

How to make the color in the "highlight" function stronger and well defined (not pale/transparent as by default) ?

Set h.EdgeAlpha = 1;

2 mois ago | 0

| accepted

How to find out isolated subgraph?

The component output in your code is the number of components. You can use the second output of conncomp to get a vector contai...

2 mois ago | 1

Find all cycles (or the initial node of each cycle) in a very large directed graph (12m nodes, 6.7m edges)

Have you tried using 'MaxNumCycles' to only compute the first 100 / 1000 / 1e4 cycles? That could give some indication if it's c...

3 mois ago | 1

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...

3 mois 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...

4 mois 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...

4 mois 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...

4 mois 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...

4 mois 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...

4 mois 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...

4 mois 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 ...

5 mois 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...

5 mois 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...

5 mois 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.

5 mois 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 ...

5 mois ago | 1

Betweenness Centrality, Edge betweenness

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

5 mois 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...

6 mois 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'...

6 mois 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. ...

6 mois 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...

7 mois 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...

7 mois ago | 5

| accepted