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Christine Tobler


Last seen: 3 días ago

MathWorks

270 total contributions since 2015

Professional Interests: numerical linear algebra, graph algorithms

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Answered
Generalized Eigenvalue Problem - Hessenberg Matrix
I agree with Steve Lord; if you're able to replicate the action of matrix A on a vector v, you can pass this to EIGS in a functi...

3 días ago | 0

Answered
Generating all non-isomorphic graphs for a given number of nodes with specified degrees
I've attached a script that computes the graphs in your example, here's the plot of all graphs it found:

4 días ago | 1

Answered
how to find kshortest path or use Dijkstra algorithm for 12 plot points.
I'm not sure how the data you're adding here maps to the picture you attached. Here's how I would go about inserting the positio...

9 días ago | 0

Answered
generate multi Diagonal matrices
The SVD is usually computed for a matrix, but you're only passing in a scalar on each call. Is it possible you meant to pass in...

18 días ago | 0

Answered
S is diagonal matrix of singular values?
MATLAB (and Fortran) store matrices in a column-first ordering, while in your file, you want to save numbers in a row-first orde...

22 días ago | 0

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Answered
Performance of matlab direct linear solver with respect to sparsity
For sparse matrices, the performance of backslash depends a lot on the specific structure of that sparse matrices (where the non...

24 días ago | 0

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Answered
How can I return real-valued eigenvectors from diagonalization?
I don't think it's possible: Looking at the eigenvalues and eigenvectors of B, >> diag(D) ans = 0.0000 + 2.0000i 0.000...

alrededor de 1 mes ago | 0

Answered
incorrect eigenvector using eig(A,B)
The residual MK*V-MM*V*w2 is expected to be numerically close to zero, however, you have to take into account the scaling of the...

alrededor de 1 mes ago | 0

Answered
highlight Nodecolor for a graph using a color map (JET)
Since colors is a n-by-3 array, use colors(i, :) to access the complete row that represents the color for node i. You can also u...

alrededor de 2 meses ago | 0

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Answered
Path between 2 nodes in a graph
Compute a path between the nodes, then check if the result is empty (this is returned by shortestpath if no path exists): path ...

2 meses ago | 1

Answered
Diagonalising a Skew-Symmetric Matrix
When EIG is called with an exactly symmetric/hermitian matrix, MATLAB falls back to a specialized algorithm that guarantees that...

2 meses ago | 1

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Answered
Properties of SVD of a hermitian matrix not holding at single precision
I'd suggest just calling EIG [V, S] = eig(A) instead of calling the SVD. If A is (exactly!) symmetric on input, this will retu...

2 meses ago | 0

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Answered
What is the difference between Gram-Smith QR decomposition procedure and qr.m function in Matlab?
MATLAB's QR decomposition is computed using Householder transformations, which is generally more numerically advantageous.

2 meses ago | 0

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Answered
Plotting a graph in layered fashion
Unfortunately, there is currently no way to do this with the 'layered' layout. I'll make a note of your need for this. For now,...

2 meses ago | 0

Answered
Shortest path through nodes
As Bjorn mentioned, this is the traveling salesman problem. The optimization toolbox has an example of how to use their intlinpr...

3 meses ago | 1

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Answered
lsqminnorm- Tolerance to Reduce Impact of Noisy Data
The tolerance in lsqminnorm should be used if you expect your matrix A to be of low rank up to a tolerance. That is, for rank k,...

3 meses ago | 0

Answered
How do I get Matlab to display a graph type data structure with decreasing weights
The Edges table attached to a digraph is always standardized so that its sorted by the EndNodes column. However, you can get a c...

3 meses ago | 0

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Answered
Ordering edge names in Digraph
The edges are reordered in the graph constructor, but it looks like the Power variable you're assigning is in the same order as ...

3 meses ago | 0

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Answered
SVD of each row of a matrix
The SVD of a row vector has the singular value equal to its norm, and the singular vectors 1 and the normalized vector. If this...

3 meses ago | 0

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Answered
qr decomposition run-time performance
When a "~" is used for a return value, this is only for code clarity. MATLAB still needs to compute that value, so the second ca...

3 meses ago | 2

Answered
Sign difference between coeff=pca(X) and [~,~,v] = svd(X)
I'm not sure why this happens. As mentioned by others, it doesn't matter what sign these outputs have. You could try stepping th...

3 meses ago | 1

Answered
How to use non-unique node names in a digraph?
Instead of setting these inputs as node names, add them as a separate variable in the nodes table. Then, pass them to the plotti...

4 meses ago | 0

| accepted

Answered
Is there any way to accelerate the solving of a series of large sparse positive definite linear equations "Ax=b" with same "A" and different "b"?
If you are able to solve for one vector using A \ b, you could pass in a matrix containing all your right-hand sides in instead:...

4 meses ago | 2

Answered
Accelerate eigs with GPU
The eigs function is not supported on the GPU. There is support for sparse matrices on the GPU, since R2015a: Release notes para...

4 meses ago | 1

Answered
Properties of adjacency matrix
In terms of the adjacency matrix, a disconnected graph means that you can permute the rows and columns of this matrix in a way w...

4 meses ago | 0

Answered
Assigning values to an array of arbitrary dimensions in MATLAB.
Using the somewhat recent implicit expansion, this can also be done without indexing into every element of the array: function ...

4 meses ago | 0

Answered
How to find all edges indexes if node indexes are given?
So you're looking for all edges where both end nodes are part of the set 4, 5, 6? This will compute them: >> [s, t] = findedge(...

5 meses ago | 0

| accepted

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...

5 meses 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.

5 meses 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...

5 meses ago | 0

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