Answered

eigen value what i am getting from matlab software that is not exact when i am compairing with hand calculated value and the mode shape i am getting is reverse

The results look correct to me, can you say what you are expecting instead? Two points that are maybe relevant: MATLAB does num...

eigen value what i am getting from matlab software that is not exact when i am compairing with hand calculated value and the mode shape i am getting is reverse

The results look correct to me, can you say what you are expecting instead? Two points that are maybe relevant: MATLAB does num...

1 year ago | 0

Answered

The node number in the digraph does not match the node number used in shortestpath().

Try putting the node numbers in quotes: [path,d, edgepath] = shortestpath(G,"228","231"); You have given each node a name, and...

The node number in the digraph does not match the node number used in shortestpath().

Try putting the node numbers in quotes: [path,d, edgepath] = shortestpath(G,"228","231"); You have given each node a name, and...

1 year ago | 1

| accepted

Answered

Unitary matrix with non-orthogonal eigenvectors?

The short answer is that it's possible to compute an orthonormal basis of eigenvectors for an orthogonal matrix, but that MATLAB...

Unitary matrix with non-orthogonal eigenvectors?

The short answer is that it's possible to compute an orthonormal basis of eigenvectors for an orthogonal matrix, but that MATLAB...

1 year ago | 2

| accepted

Answered

Eigenvalue problem on non-Hermitian matrix

You can think of it like this: If there is an invertible V such that inv(V)*H*V=D, then you can expect that the matrix myW = inv...

Eigenvalue problem on non-Hermitian matrix

You can think of it like this: If there is an invertible V such that inv(V)*H*V=D, then you can expect that the matrix myW = inv...

1 year ago | 0

| accepted

Answered

Seasonal Breakdown from a Time Series data

Perhaps the trenddecomp function would be useful? It has an optional input period where a vector of several periods can also be ...

Seasonal Breakdown from a Time Series data

Perhaps the trenddecomp function would be useful? It has an optional input period where a vector of several periods can also be ...

1 year ago | 0

Answered

How to find all the downstream nodes from a node in a graph?

Looking at this again due to the recent comment added, it might be simpler to use a directed graph instead of an undirected one:...

How to find all the downstream nodes from a node in a graph?

Looking at this again due to the recent comment added, it might be simpler to use a directed graph instead of an undirected one:...

1 year ago | 1

Answered

Which solver should I use to solve a square and symmetric, linear system of equations?

The first thing to check is the size and density of your matrix. The SYMMLQ function you mentioned is one of a group of methods ...

Which solver should I use to solve a square and symmetric, linear system of equations?

The first thing to check is the size and density of your matrix. The SYMMLQ function you mentioned is one of a group of methods ...

1 year ago | 1

| accepted

Answered

Can we compute the graph Laplacian matrix for a directed graph?

It depends how you want to define it, there is no one consistent definition of what the graph laplacian of a directed graph is. ...

Can we compute the graph Laplacian matrix for a directed graph?

It depends how you want to define it, there is no one consistent definition of what the graph laplacian of a directed graph is. ...

1 year ago | 1

| accepted

Answered

eigs using 'smallestabs' vs scalar

Hi Jack, I had initially misunderstood that you were getting different results when passing in 'smallestabs' vs. passing in the...

eigs using 'smallestabs' vs scalar

Hi Jack, I had initially misunderstood that you were getting different results when passing in 'smallestabs' vs. passing in the...

1 year ago | 0

| accepted

Answered

missing eigenvector when using eig on defective matrix

The short answer is that this is a case where a small change in the input matrix has a large effect on the eigenvectors being co...

missing eigenvector when using eig on defective matrix

The short answer is that this is a case where a small change in the input matrix has a large effect on the eigenvectors being co...

1 year ago | 1

| accepted

Answered

THE GRAPH FUNCTION DOESN'T CONSIDER WEIGHTS

Hard to say what's going wrong without seeing your code. Here's an example where you can see the weights being used to decide on...

THE GRAPH FUNCTION DOESN'T CONSIDER WEIGHTS

Hard to say what's going wrong without seeing your code. Here's an example where you can see the weights being used to decide on...

1 year ago | 1

| accepted

Answered

mldivide (backslash): advantage by using sparse matrix instead of a full matrix with respect to the quality of the results?

The condition estimate used in mldivide to decide if a warning should be given is much less accurate for the sparse case. This i...

mldivide (backslash): advantage by using sparse matrix instead of a full matrix with respect to the quality of the results?

The condition estimate used in mldivide to decide if a warning should be given is much less accurate for the sparse case. This i...

1 year ago | 2

| accepted

Answered

LDL does not support complex symmetric matrices

Largely the reason LDL doesn't support this is that it's less commonly requested for complex symmetric matrices than for complex...

LDL does not support complex symmetric matrices

Largely the reason LDL doesn't support this is that it's less commonly requested for complex symmetric matrices than for complex...

1 year ago | 0

| accepted

Answered

Inconsistency in behavior of SVD

Firstly, I agree completely with John's great explanations above: Any singular value below eps*first singular value should be tr...

Inconsistency in behavior of SVD

Firstly, I agree completely with John's great explanations above: Any singular value below eps*first singular value should be tr...

1 year ago | 3

| accepted

Answered

Accuracy Problem when solving linear equation system using: lu(S) vs. decomposition(S,'lu')

The version in decomposition does some optional steps of iterative refinement: It uses the same solution you have above based on...

Accuracy Problem when solving linear equation system using: lu(S) vs. decomposition(S,'lu')

The version in decomposition does some optional steps of iterative refinement: It uses the same solution you have above based on...

1 year ago | 0

| accepted

Answered

Need help fixing errors on code written in old MATLAB syntax

I'd also recommend replacing the calls svd(A) and svd(A, 0) with calling svd(A, 'econ'), since the code here is only using the f...

Need help fixing errors on code written in old MATLAB syntax

I'd also recommend replacing the calls svd(A) and svd(A, 0) with calling svd(A, 'econ'), since the code here is only using the f...

1 year ago | 0

Answered

Different results on different computers, Matlab 2021b - 64 bit, windows 64 bit, both Intel chips

First, about "which value to trust?" Both values are equally trustworthy, the differences in results come down to applying the ...

Different results on different computers, Matlab 2021b - 64 bit, windows 64 bit, both Intel chips

First, about "which value to trust?" Both values are equally trustworthy, the differences in results come down to applying the ...

1 year ago | 1

| accepted

Answered

eigs with Extended Capabilities

The first of these would only be useful if you need to apply EIGS to many problems in parallel, in which case each of these coul...

eigs with Extended Capabilities

The first of these would only be useful if you need to apply EIGS to many problems in parallel, in which case each of these coul...

1 year ago | 1

Answered

How to parallelize many small SVD's on a GPU

As of R2021b, there is a function pagesvd which is supported on both CPU and distributed arrays. It's not supported for gpuArray...

How to parallelize many small SVD's on a GPU

As of R2021b, there is a function pagesvd which is supported on both CPU and distributed arrays. It's not supported for gpuArray...

1 year ago | 2

| accepted

Answered

How does shortestpath function work?

Every edge has a number, which is the order in which they appear in the Edges table (try displaying g.Edges). The edgepath conta...

How does shortestpath function work?

Every edge has a number, which is the order in which they appear in the Edges table (try displaying g.Edges). The edgepath conta...

1 year ago | 1

| accepted

Answered

Eigs passes the wrong StartVector

The standard method used in EIGS is only efficient for matrices that are quite large. When eigs detects that the input matrix is...

Eigs passes the wrong StartVector

The standard method used in EIGS is only efficient for matrices that are quite large. When eigs detects that the input matrix is...

1 year ago | 0

| accepted

Answered

How to enhance the performance of Matalb's function sqrtm?

Not in general. You might be able to find a cheaper but less accurate way to compute this, but if that's acceptable would depend...

How to enhance the performance of Matalb's function sqrtm?

Not in general. You might be able to find a cheaper but less accurate way to compute this, but if that's acceptable would depend...

1 year ago | 0

Answered

fastest path between more than two nodes

To compute simply the shortest-path distance, you can use the distances function and pass in a graph object you've constructed u...

fastest path between more than two nodes

To compute simply the shortest-path distance, you can use the distances function and pass in a graph object you've constructed u...

1 year ago | 1

Answered

Follow a complex eigenvalue in a spectrum at different times

You could try using the matchpairs function: rng default; d = randn(20, 1) + 1i*randn(20, 1); d2 = d + 0.1*(randn(20, 1) + 1i...

Follow a complex eigenvalue in a spectrum at different times

You could try using the matchpairs function: rng default; d = randn(20, 1) + 1i*randn(20, 1); d2 = d + 0.1*(randn(20, 1) + 1i...

1 year ago | 0

| accepted

Answered

Error using eig in Matlab 2021b by using Parallels 17 of Macbook Pro (M1 )

Since MATLAB is trying to load a .dll file, I'm assuming you're running a Windows VM on this Macbook Pro. MATLAB doesn't support...

Error using eig in Matlab 2021b by using Parallels 17 of Macbook Pro (M1 )

Since MATLAB is trying to load a .dll file, I'm assuming you're running a Windows VM on this Macbook Pro. MATLAB doesn't support...

1 year ago | 0

| accepted

Answered

use of svds with function handles

The svds function needs to be able to apply both A*x and A'*x, so your function handle should accept a second input which is eit...

use of svds with function handles

The svds function needs to be able to apply both A*x and A'*x, so your function handle should accept a second input which is eit...

1 year ago | 2

Answered

How to compute cholesky to all slice of a tensor?

There isn't another way to do this right now. We have functions that do other linear algebra operations to each page of an ND-ar...

How to compute cholesky to all slice of a tensor?

There isn't another way to do this right now. We have functions that do other linear algebra operations to each page of an ND-ar...

1 year ago | 1

Answered

Why does mldivide solve equations so fast that FORTRAN can't compare it？

MATLAB's mldivide uses multithreading. It doesn't use the GPU unless you have the Parallel Computing Toolbox and are using the g...

Why does mldivide solve equations so fast that FORTRAN can't compare it？

MATLAB's mldivide uses multithreading. It doesn't use the GPU unless you have the Parallel Computing Toolbox and are using the g...

1 year ago | 0

Answered

How to highlight single edges in an undirected graph?

Do you still want the multiple edges to be displayed? If not, you can use the simplify command to reduce all multiple edges to j...

How to highlight single edges in an undirected graph?

Do you still want the multiple edges to be displayed? If not, you can use the simplify command to reduce all multiple edges to j...

1 year ago | 1

| accepted

Answered

Unable to find out left eigen vectors of symbolic matrix

The left eigenvectors are still expressed as right eigenvectors of M', meaning they satisfy a slightly different equation: syms...

Unable to find out left eigen vectors of symbolic matrix

The left eigenvectors are still expressed as right eigenvectors of M', meaning they satisfy a slightly different equation: syms...

1 year ago | 0

| accepted