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Christine Tobler


Last seen: 1 day ago

MathWorks

243 total contributions since 2015

Professional Interests: numerical linear algebra, graph algorithms

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Answered
Create random graph with limited degree
You could start by just making an undirected graph, and then go through each node and compute its degree. If the degree is large...

2 days ago | 0

Solved


Maximum of ND-array
Find the maximum element of a N dimensional array. Example: A=[1 2 4 ; -20 4 10]; The maximum is 10.

2 days ago

Answered
Result of A(:,:,1,1) coming as result of A(:,:,1,2)
The eigenvectors returned by EIG are returned in the same order as the eigenvalues, but the eigenvalues are not necessarily sort...

8 days ago | 0

Answered
How to find all related nodes in directed graph?
Another option is to use the weak connected components of the graph: bins = conncomp(G, 'Type', 'weak'); % bins(nid) gives th...

9 days ago | 0

Answered
rotation of graph node labels
The labels will be straight in most layouts (all but 'circle', 'layered'). You can first use 'circle' layout and then convert to...

9 days ago | 0

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Answered
Error using matlab.graphics.chart.primitive.GraphPlot/highlight>checkSubgraph
Try using Gsol = graph(idxs(ledge,1),idxs(ledge,2), [], numnodes(G)); so that G and Gsol both have the same number of nodes. T...

9 days ago | 0

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Answered
About "eigs" function
This was the case for old EIGS, it would use some random restart vectors that changed on every run. In the version of EIGS that ...

11 days ago | 1

Answered
Assign Numerical Node Labels
For the first call, use >> GG.Nodes.Name = num2str(Name)' - GG.Nodes.Name has to be a column vector. For the second call,...

13 days ago | 0

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Answered
How to find inverse of a 608*608 matrix fast?
The matrices in this file are symbolic, it's very expensive to compute with large arrays of these variables. If you cast it to f...

14 days ago | 0

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Answered
Is it possible to recover *the* decomposition that's ultimately employed by mldivide (backslash)?
The same decomposition is used, the difference is in the estimation of the condition number. MA57 provides an estimate of the co...

20 days ago | 3

Answered
"eig" use which algorithm to find eigenvalues
We don't give out the exact method used, but all syntaxes of EIG call into various LAPACK functions. See here for an introductio...

26 days ago | 0

Answered
sortrows graph edges .
The variable G.Edges.EndNodes of a graph can't be modified, it is always sorted by the nodes in the graph. This is so that the p...

30 days ago | 0

Answered
How to find all the downstream nodes from a node in a graph?
You can call nearest(G, 1, Inf) which will find all nodes reachable from node 1 in an infinite radius. This will contain only...

1 month ago | 1

Answered
Find border edges of the graph
The graph class doesn't have any functions based on coordinates of the points - it just knows about their connections. Use conve...

2 months ago | 1

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Answered
QR decomposition with the output of a permutation vector
The purpose of arranging all diagonal elements in descending order is to allow splitting R into two parts if A is low-rank or cl...

2 months ago | 0

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Answered
How to add highlighted nodes and edges of a graph to the legend?
The problem here is that legend will only provide labels for what graphics recognizes as individual objects. So in a line plot,...

2 months ago | 1

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Answered
How to restore tensor after applied the PARAFAC model?
The three component vectors represent the 3 different dimensions here. For the one-component case (all are vectors), you can use...

3 months ago | 0

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Answered
Create a graph from removed edges
The graph constructor has a syntax that specifies the number of nodes of the graph: graph(s, t, [], numnodes) if you pass the ...

3 months ago | 0

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Answered
SVD computation using eig function
Try the formula the other way around, using U_tilde, V_tilde and A to compute D: >> U_tilde'*A*V_tilde ans = 70.0118 -0....

3 months ago | 0

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Answered
Using Singular value decomposition for feature extraction from images
Image compression using SVD is a pretty common example (although not the most efficient way to compress an image), here are some...

3 months ago | 0

Answered
Error using eig Input matrix contains NaN or Inf.
The function sossolve is part of a third-party tool, this seems to be their website: http://www.cds.caltech.edu/sostools/. It's ...

3 months ago | 0

Answered
How to keep track of order eigenvalue in eig or eigs?
The eigenvalues returned by EIG are not sorted in any particular order generally (for some special types of matrices (e.g. exact...

3 months ago | 1

Answered
Eigenvectors and the null function
I'm getting those two eigenvectors when I copy your code into MATLAB: >> D = [2 -1; -1 3]; eigs = eig(D); q1 = nu...

3 months ago | 0

Answered
Block-diagonalization of a matrix
There is no direct function to do this. The best is probably to write a function that does a loop through the different blocks a...

3 months ago | 0

Answered
How created a graph from unordered node list?
When a graph or digraph is specified using numbers, the assumption is that all nodes of this graph have numbers from 1:numberOfN...

3 months ago | 0

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Answered
nonsingular matrix (X) in GSVD function
These are just different but equivalent definitions: Both will result in the same C and S, the only difference is in how X is re...

3 months ago | 1

Answered
accuracy of two methods to solve eignvalues/eignvector problem
The second way is typically more accurate, because it doesn't incur additional round-off error when conputing inv(Sw) and when m...

3 months ago | 0

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Answered
Sort eigenvectors matrix.
Take a look at rsf2csf. For a block-diagonal matrix with 1-by-1 and 2-by-2 blocks, it computes a diagonal eigenvalue matrix and ...

4 months ago | 1

Answered
Eigenvectors of an SPD matrix being saved as complex doubles
EIG does not recognize the input matrix as symmetric because it's not exactly symmetric. If you compute A = Y'*Mh*Y norm(A - A...

4 months ago | 0

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Answered
Given a matrix A^n. Comparing normal multiplication versus Diagonalization. I expect the former to be faster but its not in my case
A^2 is just one matrix multiplication, A*A, which is much faster to do directly than the call to EIG. For larger n, A^n isn't ...

4 months ago | 0

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