# Christine Tobler

### MathWorks

Professional Interests: numerical linear algebra, graph algorithms

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**Content Feed**

Eigs passes the wrong StartVector

The standard method used in EIGS is only efficient for matrices that are quite large. When eigs detects that the input matrix is...

22 hours ago | 0

How to enhance the performance of Matalb's function sqrtm?

Not in general. You might be able to find a cheaper but less accurate way to compute this, but if that's acceptable would depend...

11 days ago | 0

fastest path between more than two nodes

To compute simply the shortest-path distance, you can use the distances function and pass in a graph object you've constructed u...

16 days ago | 1

Follow a complex eigenvalue in a spectrum at different times

You could try using the matchpairs function: rng default; d = randn(20, 1) + 1i*randn(20, 1); d2 = d + 0.1*(randn(20, 1) + 1i...

19 days ago | 0

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Error using eig in Matlab 2021b by using Parallels 17 of Macbook Pro (M1 )

Since MATLAB is trying to load a .dll file, I'm assuming you're running a Windows VM on this Macbook Pro. MATLAB doesn't support...

25 days ago | 0

use of svds with function handles

The svds function needs to be able to apply both A*x and A'*x, so your function handle should accept a second input which is eit...

29 days ago | 2

How to compute cholesky to all slice of a tensor?

There isn't another way to do this right now. We have functions that do other linear algebra operations to each page of an ND-ar...

1 month ago | 1

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...

1 month 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...

2 months 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...

2 months 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 ...

2 months 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...

3 months 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 ...

3 months 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 ...

3 months 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...

3 months 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...

3 months 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;

4 months 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...

4 months 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...

4 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...

5 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...

5 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...

5 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...

6 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...

6 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...

6 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...

6 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 ...

6 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...

6 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...

6 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.

7 months ago | 0

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