# Christine Tobler

### MathWorks

Professional Interests: numerical linear algebra, graph algorithms

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**Content Feed**

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...

1 month 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 ...

1 month 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 ...

1 month 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...

1 month 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...

1 month 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;

1 month ago | 0

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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...

1 month 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...

2 months 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 months 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...

3 months 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...

3 months 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...

3 months 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...

3 months 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...

3 months 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 months 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 ...

4 months 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...

4 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...

4 months ago | 2

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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.

4 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 ...

4 months ago | 1

Betweenness Centrality, Edge betweenness

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

5 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...

5 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'...

5 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. ...

5 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...

6 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...

6 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, ...

6 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...

6 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...

7 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 ...

7 months ago | 1