Professional Interests: numerical linear algebra, graph algorithms

Answered

Soring varying and compex eigenvalues

This can't be done one the level of individual EIG calls, since it's necessary to track eigenvalues from one call to the next. T...

Soring varying and compex eigenvalues

This can't be done one the level of individual EIG calls, since it's necessary to track eigenvalues from one call to the next. T...

4 hours ago | 0

Answered

Change position of Graph edge label and node label

The position of the labels that are part of the graph plot can't be modified. It's possible to create independent text labels an...

Change position of Graph edge label and node label

The position of the labels that are part of the graph plot can't be modified. It's possible to create independent text labels an...

5 days ago | 0

Answered

Specifying node numbers using digraph

The easiest way to use graph/digraph when your node numbers are not sequential is to convert the node numbers to string, which w...

Specifying node numbers using digraph

The easiest way to use graph/digraph when your node numbers are not sequential is to convert the node numbers to string, which w...

5 days ago | 0

| accepted

Answered

Cannot create a matrix using pinv.

You've hit on a rare matrix that the SVD algorithm isn't able to work with (the SVD being the factorization called withing the P...

Cannot create a matrix using pinv.

You've hit on a rare matrix that the SVD algorithm isn't able to work with (the SVD being the factorization called withing the P...

6 days ago | 0

Answered

Solving for ALL the eigenvectors of a sparse matrix

There isn't really an algorithm like this, unless you have a very specific structure (tridiagonal or banded matrix mostly). The...

Solving for ALL the eigenvectors of a sparse matrix

There isn't really an algorithm like this, unless you have a very specific structure (tridiagonal or banded matrix mostly). The...

6 days ago | 1

Answered

How to add an edge between two nodes of two different graphs?

You could also add the edges of both graphs to one larger graph, and then use addedge to connect them. You would probably not ge...

How to add an edge between two nodes of two different graphs?

You could also add the edges of both graphs to one larger graph, and then use addedge to connect them. You would probably not ge...

8 days ago | 0

| accepted

Answered

How to make nodes' removal from a graph as a function of time?

You may want to look at the graph and digraph classes: Graph and Network Algorithms and their method rmnode specifically.

How to make nodes' removal from a graph as a function of time?

You may want to look at the graph and digraph classes: Graph and Network Algorithms and their method rmnode specifically.

11 days ago | 0

Answered

How to determine if a graph is two-connected?

The biconncomp function will split the edges of a graph into its biconnected components. If the output of biconncomp is a vector...

How to determine if a graph is two-connected?

The biconncomp function will split the edges of a graph into its biconnected components. If the output of biconncomp is a vector...

14 days ago | 0

Answered

Computing generalized Inverse of a square but sparse matrix?

If you want to apply pinv(A)*b, you can instead use lsqminnorm(A, b), which also works for sparse matrices and does something eq...

Computing generalized Inverse of a square but sparse matrix?

If you want to apply pinv(A)*b, you can instead use lsqminnorm(A, b), which also works for sparse matrices and does something eq...

17 days ago | 0

Answered

Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 9.735910e-18.

I tried plotting the following two things: >> figure; semilogy(max(abs(A), [], 1)) >> figure; semilogy(max(abs(A), [], 2)) Fr...

Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 9.735910e-18.

I tried plotting the following two things: >> figure; semilogy(max(abs(A), [], 1)) >> figure; semilogy(max(abs(A), [], 2)) Fr...

17 days ago | 0

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Answered

Modify Nodes and Edges of GraphPlot

I'm afraid that's not possible with GraphPlot. For performance, you could use scatter to plot all the nodes, and plot to plot a...

Modify Nodes and Edges of GraphPlot

I'm afraid that's not possible with GraphPlot. For performance, you could use scatter to plot all the nodes, and plot to plot a...

17 days ago | 0

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Answered

how to find out the common neighbors of two nodes in a graph?

You can use the graph class for something like this. First, make a graph from the connection inputs you had: >> A=[1 2; 1 3; 1 ...

how to find out the common neighbors of two nodes in a graph?

You can use the graph class for something like this. First, make a graph from the connection inputs you had: >> A=[1 2; 1 3; 1 ...

2 months ago | 2

| accepted

Answered

Error using tabular/permute and Error in median (line 186)

Applying median to a table directly is not supported. Either apply median to a specific variable of the table >> t = table([3;...

Error using tabular/permute and Error in median (line 186)

Applying median to a table directly is not supported. Either apply median to a specific variable of the table >> t = table([3;...

2 months ago | 0

Answered

Finding bridge of not isolated vertices

There is no functionality for MATLAB's graph class that would compute the bridges / cut edges. If performance is not a main con...

Finding bridge of not isolated vertices

There is no functionality for MATLAB's graph class that would compute the bridges / cut edges. If performance is not a main con...

2 months ago | 1

Answered

How do I stop incidence function rearranging the edges of a graph?

The reordering isn't happening when the incidence of the graph is computed, but instead at the moment that the graph is construc...

How do I stop incidence function rearranging the edges of a graph?

The reordering isn't happening when the incidence of the graph is computed, but instead at the moment that the graph is construc...

2 months ago | 0

| accepted

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...

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...

2 months ago | 0

| accepted

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:

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:

2 months 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...

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...

2 months 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...

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...

3 months 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...

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...

3 months 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...

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...

3 months 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...

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...

3 months 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...

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...

3 months 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...

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...

4 months ago | 0

| accepted

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 ...

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 ...

4 months 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...

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...

4 months ago | 2

| accepted

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...

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...

4 months 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.

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.

4 months ago | 0

| accepted

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,...

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,...

4 months 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...

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...

5 months ago | 1

| accepted