# Tag Info

Accepted

### Abrupt increase of evaluation time of MatrixExp

I think the problem is that around a dimension of 1434 or 1435, the values of MatrixExp overflow and become arbitrary precision. Perhaps the variation in the length ...
• 240k

### Abrupt increase of evaluation time of MatrixExp

(Longer comment) Usually, functions use some heuristics to determine which method to use internally. This heuristics are rarely explained, and there can be somehow unexpected jumps in performance when ...
• 29.5k

### Abrupt increase of evaluation time of MatrixExp

It becomes much faster when you use the form with vector. From help So your example becomes ...
• 148k
1 vote
Accepted

### Vector and matrix "indices" for physics calculations

If I were you and worked with Pauli spin matrices and concrete three dimensional vectors and/or two component spinors, I would make my own tool packages. For example, to compute v from q, phi, and psi,...
• 2,025

### Quadratic form derivative in Mathematica

You can use VectorSymbol and MatrixSymbol, introduced in version 14.1 as part of the Symbolic Vectors, Matrices and Arrays ...
• 29.5k

### Symbolic derivatives with vectors and matrices

Version 14.1 introduced Symbolic Vectors, Matrices and Arrays, which you can also use to calculate symbolic derivatives of vectors and matrices. ...
• 29.5k

### Get explicit formula after matrix derivation with Mathematica

Use the new-in-14.1 VectorSymbol and MatrixSymbol: ...
• 67.2k

### Calculating Matrix Derivatives

Use the new-in-14.1 VectorSymbol and MatrixSymbol: ...
• 67.2k

### Solve a time-dependent matrix DE using NDSolve

It's a bit surprising that, at least since version 12.3, NDSolve will handle the problem as expected even though the equation has actually been ruined by the ...
• 67.2k
Accepted

### How to convert a $2 \times 2$ matrix with entries of $4 \times 4$ matrices into a regular $8 \times 8$ matrix

z = ConstantArray[0, {4, 4}]; i = IdentityMatrix[4]; matrix = {{z, i}, {i, z}} // ArrayFlatten; matrix // MatrixForm  \left( \begin{array}{cccccccc} 0 & 0 &...
• 49.1k

### Solving an equation matrix with NDSolve

As of version 14.1, the problem can be easily solved with NonThreadable attribute: ...
• 67.2k
Accepted

### Central element of matrix

Assuming "better way" means better performance: Since you know the matrix has odd dimensions, you can skip Floor. Furthermore, you can calculate the index ...
• 29.5k

### Mathematica isn't returning identity matrix when multiplying matrix by its inverse

Assuming you mean Pinv := Inverse[P]; (instead of Pmatrix, which is undefined) you need to use matrix mulitplication ...
• 69.5k

### Transforming a matrix from cartesian coordinate to polar coordinate

With the corrected formula for Tc I get the following result: Could it be that the problem is related to a version of MMA? I am using version 14.0.
• 53.9k

### Replacing a column of a matrix

SeedRandom[0]; m = RandomInteger[{1, 9}, {5, 5}]; To replace one column Using ColumnMap by Michael Sollami ...
• 82.3k

Try Reduce ...
• 55.1k