Questions on the manipulation of matrices in Mathematica.

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3
votes
1answer
70 views

sorting eigenvectors of a final combined matrix

I have two matrices m1 and m2 as below: ...
1
vote
1answer
80 views

What's is the restrictions for the function MatrixExp?

When I use the MatrixExp on a general $2\times2$ matrix, Mathematica gives me this result: MatrixExp[{{a,b},{c,d}}] // TraditionalForm $\frac{1}{2\triangle}\left(...
5
votes
1answer
83 views

Would like to draw something similar to confusionMatrix created by ClassifierMeasurements

How do I show the values in each box? I know how to add the labels. Thank You
3
votes
3answers
139 views

Chopping matrix elements, real or imaginary

An undesired shape of a matrix has the following form: which is created by ...
2
votes
1answer
78 views

Mathematica's Solve[] and LinearSolve[] doesn't work to solve a system of equations IF parameters are not replaced

(I'm working on Mathematica 10.3) I have a system of 81 algebraic linear equations with 81 variables (variables are a1 to a81). ...
9
votes
1answer
226 views

Speed up construction of a dense matrix

I wish to find the numerical eigenvalues of a relatively small (100 dimensional) Hermitian matrix. While the eigenvalue calculation itself is fast, the construction of the matrix is taking longer than ...
7
votes
1answer
181 views

What kind of Arnoldi method is used in Mathematica?

Can someone give me a bit more information about what mathematical method Mathematica is using, (preconditioner, filtering-restarting, deflation) in the Lanczos implementation when I input something ...
5
votes
4answers
159 views

Add to matrix missing elements (for list of time series)

This question is an extension of the 43122. I’ve looked through many interesting post (like this) but (as always) missed the direct matching. So the setting is simple: ...
3
votes
2answers
117 views

How to form binary matrix with constants and given probability?

I want to create a binary matrix of 6x3 in which six elements (m13,m23, m33, m42, m52, m61) are constant and assigned '0' value; whereas for other twelve elements (m11, m12, m21, m22, m31,m32, m41, ...
4
votes
1answer
136 views

How to increase the evaluation speed of this somewhat complicated table / matrix operation?

I'd like to calculate the following one-dimensional array: OneDimArray = Table[(Norm[Sum[ MatrixA[[i,j]]VectorB[[j]],{j,N}]])^2,{i,N}] However this takes a very ...
3
votes
0answers
83 views

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 ...
1
vote
2answers
65 views

How to replace the selected value in matrix with a specific digit?

I want to replace the selected values through "RandomChoice" by 1 and all other values in matrix with 0. I want output in binary form matirx. ...
3
votes
2answers
136 views

Factor multiplied matrix with vector

Say I have a matrix multiplication of the form $$B=A\cdot X$$ or $$\left( \begin{array}{c} \text{a11} \text{x1}+\text{a12} \text{x2}+\text{a13} \text{x3} \\ \text{a21} \text{x1}+\text{a22} \text{...
3
votes
1answer
153 views

different situations with Compilation of ConstantArray

First, we load some tools related to Compile for analysis. ...
2
votes
1answer
88 views

Eigenvectors choose intuitive ordering/sorting

Starting from some symmetric $L\times L$ matrices $M$(see below), I want to compute the eigenvectors in Mathematica, in order to construct an ...
1
vote
1answer
55 views

Fast arithmetic on matrix elements

I have a square matrix $U$ of dimension $L\times L$, I am interested in the following quantity $U_{1,j}U_{2,k}U_{3,l}U_{4,m}\cdots U_{L,q}$ summed over all permutations of the letter indices, e.g.,...
0
votes
2answers
104 views

How to map the second highest value in each row of a matrix

I have a matrix with three or more columns called mat. I would like to map the second highest value in each row of mat into its ...
1
vote
2answers
127 views

How to parallelize this code?

Initialize a matrix a with value of $\alpha$ in central cell as "ice", and $\beta$ in every other cell. ...
13
votes
2answers
581 views

more numerically accurate inverse matrix

I encountered the following matrix mat = {{2, 2.161209223472559` + 1.682941969615793` I}, {2.161209223472559` - 1.682941969615793` I, 2}} and ...
3
votes
1answer
62 views

How to fill a tensor with matrices one by one?

I have this tensor: nn = 4; tableToFill = Table[x, {p, 1, nn}, {q, 1, nn}, {i, 1, nn}, {j, 1, nn}]; that I want to fill with a matrix one by one with a matrix ...
3
votes
0answers
52 views

FindInstance of Matrices

I'm trying to use FindInstance to find examples of matrices that complete an expression. However, it seems like I need to specify atomics as my variables to the function. So, here's a really simple ...
0
votes
0answers
57 views

Can't operate on vector within a list of rules

I'm trying to set up a list of rules which includes the following: ...
0
votes
0answers
47 views

LatticeReduce question

Does LatticeReduce work with arbitrary precision arithmetic? That is, if I give it a linearly independent integer basis, but the integers are 40 decimal digits long ...
6
votes
2answers
152 views
3
votes
1answer
141 views

FindMaximum “is not a real number at” nrnum problem

I'm experiencing a problem using FindMaximum that I don't understand (due to my newbie knowledge of Mathematica's syntax). That is, FindMaximum sometimes returns a (correct) answer, but sometimes ...
0
votes
1answer
121 views

Generate random Hermitian matrices [duplicate]

I want to generate random Hermitian matrices. For now, random Hermitian matrices with size 2 are obvious to construct. But elegant methods for higher dimension would be nice! Are there methods besides ...
0
votes
0answers
34 views

Handling a matrix with components greater than machine precision

I have four quantities stemming from a 4th order differential equation. I can represent these as a vector which is a product of a 4X4 matrix $$ M=\left\{v,\frac{\partial v}{\partial x},\frac{\partial ...
6
votes
2answers
72 views

A problem about matrix/vector extension via $\tt ArrayPad$

Given that I have a vector and matrix as follow: vec = Array[Subscript["P", #] &, 6, 0]; mat = Array[Subscript["P", #1, #2] &, {5, 4}, {0, 0}]; And I ...
2
votes
1answer
60 views

Eigenvalues are not the same in the special case

I have this matrix: h = { {e1, 2, x}, {2, 2, x}, {x, x, 2} }; I want to calculate the eigenvalues and then set x equal to zero: ...
6
votes
1answer
71 views

Matrix Multiplication after “Flatten”

Say we originally had two matrices, $A$ and $B$, both $n \times n$, whose product $$ C= A.B $$ Now I flatten $A$. I can obtain a flatten $C$, from the following multiplication $$ C_{flat}=A_{flat}....
6
votes
1answer
121 views

List consisting of positions of the matrix elements and the elements themselves

Given a 2D matrix I would like to make a list with elements consisting of positions of the matrix elements and the elements themselves. Let the matrix be ...
3
votes
3answers
118 views

How can I make custom accumulated sequences like the following?

First of all, I don't really know how to formulate the question, so if you understand my question and know a better way to phrase it, please revise. I have the following Matrixes: ...
2
votes
3answers
81 views

How can I create a dynamic Matrix inside a function?

I have a function where a n parameter is handed and a list of values is calculated inside of it. I then need to solve a linear system of equations that require me ...
3
votes
1answer
67 views

How to multiply a row to multiple rows in a matrix

I have the Following Matrixes; ...
0
votes
1answer
110 views

Precision of Eigensystem? [closed]

I was using Eigensystem to obtain the rotation matrix. However, I find out Mathematica does not fully diagonalize my matrix (or say not precise enough). My matrix ...
1
vote
1answer
100 views

Visualizing Matrix that represents a network

I have a nxn matrix $A$ that represents a network. I have $n$ nodes in the network, and the matrix $A$ represents the number of connection (edges) between the different nodes. For example, if $A$=0, ...
0
votes
1answer
67 views

errors in simple for loops

Im trying to run the following code, which I have translated from Matlab. I created a for loop nested inside another for loop. mW is a matrix, and ...
0
votes
1answer
47 views

Output of Coefficientrules into Jacobian matrix

I have a pair of large polynomials in u, v, a1...a9 and b1...b9, generated by ...
0
votes
2answers
49 views

Enlarge a matrix and fill in zeros [closed]

Suppose I have a dynamically generated 4-dimensional matrix L in the shape shape={d1, d2,d3,d4}, and ...
0
votes
1answer
42 views

Tolerance of PositiveSemidefiniteMatrixQ [closed]

I believe the following should be True but returns False for me: ...
2
votes
2answers
73 views

Reliably computing the signature of a matrix with small eigenvalues

When asked to compute the eigenvalues of the following matrix ...
4
votes
2answers
141 views

Extract part of a matrix

I have imported a matrix from a .txt file (it could be better from an Excel file): ...
4
votes
1answer
206 views

how can i associate the headings of columns/rows with content of itself and then recall what i want after i've imported the excel file in mathematica

Hello, i make another try... I have to import a file like this below (it is an excel file, i show you just the beginnig. it should have thousend of rows and columns). After i've imported the file i ...
2
votes
1answer
58 views

Interpret hexadecimal sequence as a binary matrix that can be used in AdjacencyGraph

I have a database of hex sequences stored as blob. Each of them is a binary matrix representing the adjacency matrix of a directed graph. I want to use the ...
1
vote
0answers
61 views

Calculating in the group ring $Q[GL_n(Z)]$

I am trying to use Mathematica to check some identities in the group ring $Q[GL_n(Z)]$. Is there a package/function of Mathematica to do this? Thanks a lot in advance!
4
votes
3answers
172 views

How to plot real roots of complex polynomials avoiding branch cuts?

Lets say I have the following matrix: M={{1,3+E^(I x),-1+2I x},{3+E^(-I x),2,E^(3I x)},{-1-2I x,E^(-3I x),-2}}; $$ M=\begin{pmatrix} 1& 3+\mathrm e^{ix} &...
3
votes
2answers
130 views

Take a specific part of a matrix imported from a .xls

i would like to know if there are any ways to link headings of a table i had imported with the data in the table itself. I imported a matrix from an excel file and i want to take a specific part of it....
15
votes
5answers
551 views

A quicker than outer

I need to get a matrix $\{a(x_i-x_j)\}$, where $x_i$ form a partition of an interval, $a(x)$ is a given function. I use ...
-1
votes
1answer
91 views

Is it possible to colour only one column of a matrix? [closed]

I was wondering if it's possible to colour a column or a row in a matrix. For example is it possible to add colour for one of the rows/columns of the following matrixform code? ...
2
votes
5answers
381 views

Create a Pascal Matrix

I am trying to write a function that can create a Pascal matrix. So far I have ...