Unanswered Questions
431 questions with no upvoted or accepted answers
13
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What algorithm is Mathematica using to find the smallest eigenvalue so quickly?
My question is what kind of black magic is Mathematica doing to obtain the correct answer so quickly compared to other programming languages?
Details:
I've written a Mathematica notebook to find the ...
11
votes
0
answers
856
views
How to speed up calculations on big symbolic matrices?
this is my first time posting something on a community of the StackExchange platform, so please feel free to correct me if I'm doing something wrong. :) Additionally you should probably know that I'm ...
- 275k
10
votes
0
answers
279
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Bug in PositiveDefiniteMatrixQ?
Fixed in 10.1.0.
Exists in at least 9.0.1 -- 10.0.2.
This seems like a bug in PositiveDefiniteMatrixQ to me:
...
9
votes
0
answers
233
views
Symbolically evaluating gradients/Hessians
I'm taking a machine learning course, which involves taking a lot of analytical gradients and Hessians. It would be ideal if I could perform these calculations in Mathematica. However, I am only aware ...
- 91
8
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0
answers
227
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Why has Version 10.3 precision reduced?
In version 7.0.1.0 and versions 10.0 and 10.1 the following is produced:
...
7
votes
0
answers
241
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Differing behavior of Eigenvalues and Eigensystem
With the update to v12.0, I seem to be getting different behavior of eigenvalues returned by Eigenvalues and Eigensystem (oddly, ...
CommunityBot
- 1
7
votes
0
answers
635
views
Inverse of a large sparse Hermitian block matrix
I am looking for a method (if it exists) for the inverse of a large sparse Hermitian block matrix.
The off diagonal sparse matrices, named δ are 4x4, and they have ...
- 66.4k
6
votes
0
answers
271
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Solving a matrix pencil (quadratic eigenvalue) problem with Mathematica
According to Wikipedia
The matrix pencil of degree $\ell$ is the matrix-valued function
defined on the complex numbers $L(k) = \sum_{i=0}^{\ell} k^{i} A_{i}$.
Here $A_{\ell}$ are non-zero $n\times n$...
CommunityBot
- 1
6
votes
0
answers
120
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Where is the mistake in computing the particular eigenvector of the following DFT Matrix?
I have the following matrix (the DFT Matrix for N = 3)
$$W = \frac{1}{\sqrt{3}}\begin{pmatrix} 1 & 1 & 1 \\ 1 & e^{-\frac{i 2 \pi}{3} } & e^{\frac{i 2 \pi}{3} } \\ 1 & e^{\frac{...
6
votes
0
answers
226
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MatrixPower performance
In Mathematica 9, (I think) MatrixPower[matrix(m.m), n].vector has complexity $O(m^{2+\epsilon}\times\log(n))$ (Mathematica automatically find the algorithm that ...
6
votes
0
answers
2k
views
Export matrix to $\LaTeX$ with style
Is it possible to export a matrix to $\LaTeX$ with style?
For example this code will create a matrix with equal spacing matrix and with background colors in some cell, is it possible to export that ...
- 3,680
5
votes
0
answers
317
views
How to efficiently apply PCA followed by SVD to extract the components of PCA?
I am working on segmenting a textured image using Gabor Filters. This is based on this paper. There exist a Matlab implementation of this as well. Earlier I managed to do up to this. With the help of ...
- 3,435
5
votes
0
answers
299
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Is Mathematica a good choice for a scientific project with Machine Learning?
I'm a chemist with some rudimentary programming skills and in the middle of the year I'll be starting a project concerning machine learning, so, I'm sorry if I'm going to ask two questions in this ...
- 193
5
votes
0
answers
875
views
Finding eigenvalues in Mathematica: why so slow?
I am trying to find the eigensystem of a large sparse real symmetric matrix, and I only need the lowest 40 or so eigenstates. The relevant code is as follows:
...
5
votes
0
answers
474
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Real Canonical Form of Arbitrary Size Matrices
I have been searching the site and the Mathematica documentation, but have not found anything regarding this.
If we find the Jordan Form of the following matrix, we get complex values, but I would ...
CommunityBot
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