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Christine Tobler

MathWorks

181 total contributions since 2015

Professional Interests: numerical linear algebra, graph algorithms

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could anyone help me to calculate the euclidean distance for the matrix.
Hi Bruno, I have the same problem where I can't comment on your answer, so adding another answer here. That's a good point - ve...

23 giorni ago | 0

could anyone help me to calculate the euclidean distance for the matrix.
For MATLAB R2017b or later, you can use the vecnorm function for a simpler construction than the one involving sqrt, sum, and .^...

circa un mese ago | 1

Hi just want to know if someone can maybe help me i have this matrix t want to get the eigenvector but it give me complex values and im pretty sure it must not be complex values for that matrix
A simple way to verify if the returned eigenvalues are correct is to compute both the eigenvalues and the eigenvectors, and to c...

circa 2 mesi ago | 1

How can I solve a sparse linear system efficiently in MATLAB?
Do you need the whole matrix A*inv(B)*A', or do you just need to apply this matrix to a vector (A*inv(B)*A'*x)? In the second ca...

2 mesi ago | 0

Backslash (\) operator became much slower when updating from 2015b to 2019a
Thank you for these logs. The difference in behavior comes from the following message, saying that we repeat the factorization w...

3 mesi ago | 1

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Backslash (\) operator became much slower when updating from 2015b to 2019a
Based on the spy plot, I would be astonished if a different method was selected between the two releases - I think the LU solver...

3 mesi ago | 1

Backslash error ''Warning: Matrix is singular to working precision."
For more details about what backslash does for sparse matrices, use spparms('spumoni', 1) cnew = Amat \ rhs; This will displa...

4 mesi ago | 1

SVD freezes in 2018a
This sounds like a bug. It shouldn't be due to memory issues, SVD uses the same amount of memory if the matrix size and the synt...

4 mesi ago | 0

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generalized eigen-problom, complex non-symmetric matrix, how to find orthogonal eigenvectors
There's an easier way to compute both U and W: [U, D, W] = eig(A, B); This will make sure that the eigenvectors U(:, i) and V(...

4 mesi ago | 1

Optimizing a matrix with cplexlp?
You can solve this using intlinprog. This is probably not the most efficient way of solving the problem, but reliable A = [0 1 ...

4 mesi ago | 1

How SVD works for dimensionality reduction?
There's the svd function. The link points to the doc which has examples of how to use it.

5 mesi ago | 0

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chol fails on Hermitian positive definite matrix?
That is astonishing. The matrix is not badly conditioned, I would expect CHOL to work fine here. I tried on my machine and didn...

5 mesi ago | 0

| accepted

Sparsest solution for A\B
That statement is wrong, x = A\b doesn't return the solution x with the smallest number of nonzero elements. What mldivide does,...

5 mesi ago | 2

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eigs function: incorrect eigenvalues
The problem is that the matrix A is badly conditioned: >> cond(full(A)) ans = 2.206837183464466e+16 This is just around...

5 mesi ago | 2

Plotting eigenmodes in 3D
Depending on the format of your 3D-frame, maybe you could use pdeplot3d.

5 mesi ago | 0

matchpairs function in r2019a
The algorithm solves the same problem as the Hungarian algorithm, but it's not the same algorithm. The Hungarian algorithm has c...

6 mesi ago | 0

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Hungarian algorithm realizated in matlab
As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

6 mesi ago | 0

Hungary algorithm
As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

6 mesi ago | 1

Matching of eigenvalues of 2 matrices
With R2018a, there is a new function matchpairs which might be useful for this. Basically, it takes a matrix of similarities bet...

6 mesi ago | 0

| accepted

How to calculate n-th eigenvector using eigs() function
There's no way of doing this directly, and the indirect ways are hard to implement and not very robust. Also, this will be very...

6 mesi ago | 2

| accepted

Simulating a Markov chain
There is a specific class that represents a discrete-time Markov chain in the Econometrics toolbox: dtmc.

6 mesi ago | 0

Delete Highlighted Node in a Graph?
You can use highlight to set that marker to 'none'. The GraphPlot object h contains all the graphical properties of the plotted ...

6 mesi ago | 0

| accepted

Yet another lu(A) question and pivoting
I'm afraid I can't post the algorithm used in mldivide. Note that it's a bit more general: it also works if both the rows and th...

6 mesi ago | 0

Yet another lu(A) question and pivoting
Yes, MATLAB checks if L is a permuted triangular matrix. See the doc for mldivide - Algorithm for full inputs. However, it's st...

7 mesi ago | 1

In sparse matrix eigs(A,k,sigma), how to specify both shift and direction
With a numeric sigma, EIGS uses a linear system solve (A-sigma*I)\v instead of A*v to compute the largest eigenvalues of the inv...

7 mesi ago | 0

| accepted

Is there a way to obtain all cycles of a directed graph similar to all_simple_cycles() in sage?
There's no direct function, but I've attached a solution I've quickly put together just now. This recursively iterates through a...

7 mesi ago | 0

How to generate all the matrices of graphs for given numbers of vertices and edges?
I've attached a script that computes this for n=4 and e=3. This script will not scale well to larger numbers of nodes and edges,...

7 mesi ago | 0

Which algorithm eig () function use ?
There are different algorithms for solving eigenvalue problems, depending on the properties of the inputs. The most well-known s...

7 mesi ago | 0