# Christine Tobler

### MathWorks

Professional Interests: numerical linear algebra, graph algorithms

**Statistics**

RANK**102**

of 279,927

REPUTATION**1,220**

CONTRIBUTIONS

**0** Questions

**383** Answers

ANSWER ACCEPTANCE **
0.00%
**

VOTES RECEIVED**241**

RANK

of 18,776

REPUTATION**N/A**

AVERAGE RATING**0.00**

CONTRIBUTIONS**0** Files

DOWNLOADS **0**

ALL TIME DOWNLOADS**0**

CONTRIBUTIONS**0 Posts**

CONTRIBUTIONS**0** Public Channels

AVERAGE RATING

CONTRIBUTIONS**0** Highlights

AVERAGE NO. OF LIKES

**Content Feed**

How can I plot a multilayer graph (2 layer) starting from adjacency matrices?

Here's an example of how to do this (using just some random data, since I don't have the matrices you mention above). % Choose ...

2 months ago | 1

| accepted

How to create a random graph that is connected?

If an undirected graph is connected, it must contain at least one path that visits each node at least once. You could construct...

2 months ago | 0

I have a question about the distributed computing of the eig function.

EIG for distributed arrays calls into the ScaLAPACK library - the references given by ScaLAPACK documentation would be the best ...

2 months ago | 1

| accepted

non linear eigen value problem

This isn't the standard definition of a nonlinear eigenvalue problem, where you would have only one scalar lambda. Am I underst...

2 months ago | 0

Issues with the normalisation of mode shapes?

eig(A, B) normalizes the eigenvectors in the B-mass norm, but only if it recognizes the input as a symmetric problem (A is symme...

4 months ago | 0

| accepted

Proof of relation between the generalized singular values of gsvd(A,B) and gsvd(B,A)

The background for this is the 5-output form of the GSVD: [U,V,X,C,S] = gsvd(A,B) returns unitary matrices U and V, a (usually)...

4 months ago | 0

Update a sparse matrix efficiently

The fastest way to construct a sparse matrix will be when the inputs are sorted, first by columns and then by rows. You can veri...

4 months ago | 0

Given a big square matrix and some eigenvalues, how to find the corresponding eigenvectors?

I wouldn't expect a 3072-by-3072 matrix to be a problem on the machine you describe. Could you try to run the following on your ...

5 months ago | 0

| accepted

new interface for QR decomposition in Matlab 2022a

Yes, we made this change for R2022a. I'm sorry this has caused problems for you, @Klaus Diepold, could you share how you had bee...

6 months ago | 1

how to find eigenvalues using the determinant ?

The determinant should only be used explicitly to solve an eigenvalue problem for symbolic calculation (for example, when you so...

7 months ago | 2

| accepted

GUI crashes when using eigs with a nonzero shift on a large generalised eigenvalue problem.

Ideally this shouldn't crash, but produce an out-of-memory error. However, for example on Linux there is the "out-of-memory kill...

8 months ago | 0

| accepted

GPU speed up for pcg() is disappointing

It looks like you can simply replace your current call to pcg with x = pcg(A, b, tol, 5000, @(y) L\y, @(y)L'\y); as the error ...

9 months ago | 0

What is matlab doing under the hood when I solve this generalized eigenvalue problem?

You can use the Display option to get some more information on what's going on inside of eigs. load matrices.mat [V,D] = eigs(...

9 months ago | 1

| accepted

Trapz error in calculating 2D integrals: ORDER contains an invalid permutation index

Replace the line I = cumtrapz(y,cumtrapz(x,MBerry(keySet),2)); with I = cumtrapz(y,cumtrapz(x,MBerry(keySet),2), 1); Here'...

9 months ago | 0

`svd` sometimes blows up - how to fix it?

In short, the problem is that pinv_modified is based on a misunderstanding of the workaround here. The idea is to check if SVD f...

10 months ago | 1

Calculating node coordinates for a graph without plot command

Unfortunately there isn't a way to get these coordinates without plotting. I have added your request for such a function to our ...

10 months ago | 1

| accepted

'MarkerEdgeColor' for Graph/Digraph Nodes

Yes, MATLAB's graph and digraph plots only have one NodeColor property which applies to both the marker's FaceColor and EdgeColo...

10 months ago | 0

How to convert a graph / edges list into a shapefile (.shp) ?

There isn't a direct way to do this with a graph object. The mapping toolbox has a shapewrite function which produces a .shp fil...

11 months ago | 0

Condition number of empty matrix

The case of a 0-by-0 matrix doesn't have any very useful definition, as you note correctly in the comments above. MATLAB does w...

11 months ago | 1

| accepted

How to fix **Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 1.053110e-20.** ?

Yes, the matrix A becomes singular after applying the last two for-loops (which I think are the boundary conditions). You can v...

1 year ago | 1

How to check if there is an edge between two nodes in an undirected graph?

Call findedge(g, node1, node2). If there is no edge connecting these nodes, the output is zero. Otherwise, the output is the ind...

1 year ago | 0

| accepted

Why does lu function yield different lower triangle matrix if I return [L,U] rather than [L, U, P]?

The LU decomposition really involves three new matrices: An upper-triangular matrix U, a lower-triangular matrix L, and a permut...

1 year ago | 0

| accepted

How to find a permutation matrix to turn a general hermitian matrix into a block diagonal one?

First, we should keep in mind that the task is really to find a representation of A with as small blocks on the diagonal as poss...

1 year ago | 0

| accepted

Interpreting eigenvalues and eigenvectors when using symbolic toolbox

I'm getting both 4 eigenvalues and 4 eigenvectors when running your code: linkMatrix = [0,1/3,1/3,1/3; 0,0,1,0; ...

1 year ago | 0

| accepted

Different behaviour in indexing between table and digraph node table

This is a bug in digraph, thank you for reporting it! I have passed it along and it will be fixed in a future release.

1 year ago | 0

| accepted

Linking nodes using links in a graph based on information from another layer

You could represent the first layer as a graph object, adding coordinate information for each node to the Nodes table. For the s...

1 year ago | 0

Error message when trying to compute EOF with covariance matrix.

The problem is that the covariance matrix becomes very large here. Luckily, it's not necessary to compute this matrix explicitly...

1 year ago | 0

| accepted

Sorting eigenvectors using symbolic toolbox for PageRank algorithm

There's an unknown variable in the value you pass to sort, so this won't be sorted by magnitude as the magnitude isn't known. H...

1 year ago | 0

| accepted

eigenvalue and eigenvector of free vibration while stiffness matrix is not invertable

If eig has been working well for the size of your problem you could consider using [U, D] = eig(K, M); %this solves K*U = M*U*D...

1 year ago | 1

| accepted

Finding a node in graph with most mutually adjacent nodes

Thanks for adding the tag, Steve! Here's another idea for how to do this. So you want to find all pairs of edges that go a->b a...

1 year ago | 1

| accepted