Questions on the manipulation of matrices in Mathematica.
6
votes
0answers
228 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 ...
16
votes
3answers
1k views
How to symbolically do matrix “Block Inversion”?
Consider a block (partitioned) matrix
matrix = ArrayFlatten[{{a, b}, {c, d}}]
where, a, ...
3
votes
1answer
252 views
Take[] and other Mathematica functions with live streams
I have a live video feed that I would like to convert into raw numbers that could be used for a variety of different things. I would also like to do simple operations on these numbers live with as ...
29
votes
6answers
2k views
Does Mathematica have advanced indexing?
I have two $M \times K$ arrays $L, T$ where I would like to set all the elements in $L$ to zero whenever the corresponding element of $T$ is greater than 15. The ...
10
votes
2answers
553 views
Non-commutative symbolic linear algebra
I am fairly new to Mathematica but I thought I would be a helpful tool to carry out a few simple linear algebra calculations. It seems like an easy task but I cannot figure out how to do it. For ...
8
votes
1answer
696 views
Bordermatrix from LaTeX
How would I create an output similar to the result produced by this LaTeX code:
...
14
votes
2answers
473 views
Using the Krylov method for Solve: Speeding up a SparseArray calculation
I'm trying to implement this Total Variation Regularized Numerical Differentiation (TVDiff) code in MMA (which I found through this SO answer): essentially I want to differentiate noisy data. The full ...
4
votes
1answer
61 views
Trouble using FindInstance with MatrixRank
I'm really confused about what's going wrong with my call to FindInstance:
...
2
votes
3answers
573 views
Orthonormalization of non-hermitian matrix eigenvectors
When using Orthogonalize[] one can specify which definition of "inner product" is to be used. For example, ...
7
votes
3answers
323 views
Add lists with unequal lengths together to create a matrix
I'm trying to create a stacked bar chart using raw data coming from a MySQL server. The result coming back from one query is:
...
6
votes
0answers
219 views
MMA implementation of Earth Movers Distance?
Has anyone implemented in MMA the Earth Mover's Distance (EMD)? A concept dating back to Monge 1871, used to compare histograms and images, e.g., the CIEDE2000 Color Difference algorithm. Yossi ...
15
votes
4answers
431 views
How do I generate the upper triangular indices from a list?
I have some list
{1,2,3}.
How do I generate nested pairs such that I get
{{1,2},{1,3},{2,3}}?
That is I'd like a way to ...
6
votes
2answers
372 views
Entering block matrices for an arbitrary matrix size
Background: How to enter matrices in block matrix format? and the following:
I want to create
$$
f(A,t) = \left [
\begin{matrix}
A & t \\
0 & 1
\end{matrix} \right ]
$$
where $A$ ...
4
votes
3answers
463 views
Trying to simplify Root expressions from the output of Eigenvalues
I am trying to calculate eigenvalues of a sparse matrix with only two distinct non-zero elements, here Alpha and Beta, which are both negative reals. Mathematica returns some complex expressions with ...
1
vote
0answers
240 views
Matrix multiplication involving MatrixForm [duplicate]
Possible Duplicate:
Why does MatrixForm affect calculations?
I am doing a matrix multiplication, but not getting the desired output. I am doing the matrix multiplication of $A^{-1}B$ from ...
3
votes
4answers
3k views
Creating a table/Matrix during a For loop
I have a For loop (with i as a counter), which calculates different values (y1, ...
9
votes
4answers
1k views
How can I multiply matrix and vector element wise like Numpy?
I have an $M \times K$ matrix $C$ and a length $K$ vector $v$. I want to form the $M \times K$ matrix $S$ where $s_{ij} = C_{ij}/v_j$. To do this in numpy I simply divide the two objects like this
...
16
votes
3answers
297 views
How to improve this code for exploring large matrices?
What I'm actually trying to do is to elaborate this question. I'd like to use Pane with scrollbars enabled to explore large (sparse) matrices like this one:
Here ...
12
votes
4answers
632 views
What is the right way to rotate an array?
Suppose I have an array, not necessarily square:
a = $\left(
\begin{array}{ccc}
1 & 2 & 3 \\
4 & 5 & 6 \\
7 & 8 & 9
\end{array}
\right)$
I want to rotate it like one ...
10
votes
1answer
344 views
Nesting Parallel processes
I just attempted to run code that had nested ParallelMap[] functions. It generates the error message:
ParallelMap::subpar: Parallel computations cannot be nested;
proceeding with sequential ...
7
votes
1answer
477 views
How to apply a permutation to a symmetric square matrix?
Given a symmetric square matrix, how can I apply a permutation to the rows and columns (i.e. the same permutation to both the rows and the columns) such a way that the new structure of the matrix ...
5
votes
1answer
790 views
Simpler way of performing Gaussian Elimination?
Is there a simpler way of performing Gaussian Elimination other than using RowReduce? Such as a single built in function?
Edit: Look at the example from our simulation class. Not too difficult, but ...
12
votes
4answers
499 views
What is the fastest way to locate an image inside a larger image?
let b =
let c =
How to do:
find[c,b]
that returns the bounding box of c in b?
...
14
votes
2answers
972 views
How to enter matrices in block matrix format?
Example:
I have a matrix $R = \left( \begin{array}{cc}
A & \mathbf{t} \\
0 & 1 \end{array} \right) $ where $A$ is 3-by-3 and $\mathbf{t}$ is 3 by 1. Or in Mathematica
...
4
votes
2answers
325 views
Why don't * and ^ work as I expected on matrices?
For example, this input...
{{1, 2}, {3, 4}}*{{1, 2}, {3, 4}}
produces this output...
{{1, 4}, {9, 16}}
and this input...
...
19
votes
5answers
957 views
What is the most efficient way to add rows and columns to a matrix?
Say I have a matrix m and a vector v.
...
