Questions on the manipulation of matrices in Mathematica.

learn more… | top users | synonyms (1)

0
votes
1answer
115 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 ...
2
votes
2answers
580 views

Get inverse of a matrix step-by-step [duplicate]

How can I get the inverse of a matrix step by step? An example: Given the matrix `{{8, 2}, {3, 2}}´, the result is {{$\frac{1}{5}$, -$\frac{1}{5}$}, {-$\frac{3}{10}$, $\frac{4}{5}$}}. But how can I ...
7
votes
1answer
190 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 ...
0
votes
4answers
129 views

Constructing an arbitrary dimensional matrix with a certain rule

I want to construct the following matrix $M$ of dimension $(N+1)\times(N+1)$ with the following rule (for arbitrary N). Below, in the subscript, as usual, the 1st index gives the row and the second ...
12
votes
7answers
650 views

Brackets around each item in matrix

I have a matrix where every item in the matrix has its own brackets that I do not want. How can I remove the brackets around each item?
3
votes
0answers
197 views

Mathematica's Singular Value Decomposition different from another math engine [closed]

I’ve been working with SVD – singular value decomposition. Things weren’t working as expected. Thus, I looked over to Matlab and executed the following code: ...
3
votes
2answers
794 views

How do I get the inverse of a homogeneous transformation matrix?

I want to get the inverse of this homogeneous transformation matrix: iab = { {1, 0, 0, 0}, {0, 0, -1, 0}, {0, 1, 0, 3}, {0, 0, 0, 1} } ...
2
votes
1answer
164 views

Simple code to write differential equations in a matrix formulation

Is there a simple code to transform the following differential system equations : ...
9
votes
1answer
116 views

UnitaryMatrixQ function not returning true for a unitary matrix

So I know this matrix is unitary. It's a well proven fact in quantum mechanics and you can even check for yourself on pen and paper, Heres a quick proof: Assume $H$ is hermitian (i.e. $H^\dagger=H$) ...
1
vote
2answers
124 views

Update: Calculate Tensor products and traces with Mathematica

My goal is to algebraically simplify expressions involving tensor products and taking the trace. That is, I would like to compute $\operatorname{Tr}\left( \prod_i(id+a_i \otimes b_i) \right)$, using ...
1
vote
1answer
48 views

Array Flattening arrays of matrices given by rules

Fix an $n$ and an $m$ positive integers.I have some set of four $n\times n$ matrices $A$,$B$,$Y$,$Z$ (where $Z$ is the zero matrix). I'd like to input the $nm\times nm$ matrix of block matrices given ...
1
vote
0answers
29 views

MatrixForm in Mathematica [duplicate]

I wanted to do subtractions between to matrices and I did the following ...
0
votes
1answer
83 views

what do those signs #1, #1^2, #1^3, & mean here? [duplicate]

I have read common pitfalls page and the documentation page but I still don't understand what do those signs mean here? ...
-7
votes
2answers
71 views

How to solve for the eigenvalue in matrix? [closed]

For which value of $a$ in the matrix {{a,2}, {3,4}} has the matrix eigenvalue of $0$? How to solve it in Mathematica?
3
votes
1answer
78 views

Calculating products of given length of two matrices

I have the following problem to solve. Let us have two given square matrices $A$ and $B$ of the same size and a positive integer $n$. I would like to produce all products of length at most $n$ of ...
7
votes
1answer
206 views

Incorrect Left and Right Eigenvectors in Mathematica

I'm trying to find the Left and Right Eigenvectors of a pretty straightforward matrix, but Mathematica doesn't seem to be able to do it for even a 200 dimensional matrix. Background: Given an ...
4
votes
3answers
1k views

Orthonormalization of non-hermitian matrix eigenvectors

When using Orthogonalize[] one can specify which definition of "inner product" is to be used. For example, ...
2
votes
1answer
34 views

Encoding/Decoding matrices as integers, integers as matrices [closed]

I want to convert large binary matrices of m x n dimensions into integers, and then to convert these integers to the original matrices. I attempted the following: ...
1
vote
1answer
66 views

Monitoring a matrix with changeable elements as Manipulate in plotting [closed]

If we remember, Mathematica has an ability to show a Psudo-window of plots for monitoring the effects of some changeable parameters in the functions. For example ...
0
votes
2answers
83 views

Flipping random elements in a matrix

I'm still a beginner with mathematica so maybe the solution is obvious, but for some reason my code that worked fine earlier doesn't work now. I haven't changed anything about it. I've restarted ...
2
votes
2answers
116 views

plotting eigenvalues with devoted level coloring

I am about to plot eigenvalues of a matrix versus varyingj's. ...
6
votes
1answer
75 views

Constructing a particular Toeplitz matrix with a certain rule

I want to construct a Toeplitz matrix in Mathematica. Usually it is done in Mathematica using the following command: ToeplitzMatrix[{a,b,...},{a,y,...}] I want ...
5
votes
3answers
240 views
0
votes
1answer
35 views

What is the function “oneflag_:0” in this expression? [closed]

The first function Pivotdown can zero out all entries in a column below a desired location. But l don't know the function of “oneflag _0".
1
vote
1answer
62 views

Generate a simulated covariance matrix

I am working on a problem where one of the input variables is the level of covariance between the entries in a particular matrix. To simulate this problem in Mathematica, I will need to feed my code ...
4
votes
1answer
62 views

Computing the logarithmic spectral norm rapidly

I wish to compute the logarithmic spectral norm of a square matrix $A$, which is defined by \begin{equation} \mu_2[A]=\lim_{t\downarrow0}\frac{\|I+tA\|_2-1}{t}. \end{equation} Hence, I simply code ...
1
vote
1answer
225 views

What is the fastest way to obtain the eigenvalues of a Wishart matrix?

I would like a fast method of creating a sample of random numbers which corresponds to the eigenvalues of a Wishart matrix: For M>N the eigenvalues \lambda_i are given by the jpd Where $K_N$ is ...
3
votes
1answer
153 views

Hasse Diagrams from Adjacency Matrix

Let's say I have a rather large adjacency matrix for a partial order relation. Say an 80x80 matrix. What is the best way to display Hasse diagram? I have tried AdjacencyGraph and it does a not so bad ...
0
votes
1answer
34 views

Picking some elements of a matrix and generating another matrix [duplicate]

If we have a nested matrix as: start={ {{1, 2, 2, 3}, {1, 1, -2, 1}, {3, 2, 2, -I}, {1, 2, 0, -I}}, {{3, 4, 4, 0}, {1, 1, 4, 1}, {3, 3, 4, -1}, {1, 1, 2, I}} } ...
1
vote
1answer
414 views

Factor vector out of a matrix

I am wondering how to factor a[1],a[2],...,a[4] out of sim so that I can write sim as the ...
2
votes
1answer
37 views

wrong result of an iteration related to replacement and comparing

We have two nested matrix and a code for replacement following an equality as: ...
4
votes
2answers
98 views

replacement in a nested matrix

We have a nested matrix m1 = {{{1, 2, 2, I}, {1, 1, -2, 1}, {3, 2, 2, -I}}, {{3, 4, 4, I}, {1, 1, 4, 1}, {3, 3, 4, -1}}}; we must replace the first number of ...
1
vote
3answers
123 views

Conditionally binarizing matrices

I want to (fastly) convert matrices with values that are <= a threshold to binary matrices. I used a call to Binarize, but I don't like the Image and ImageData conversions as they obfuscate the ...
2
votes
1answer
64 views

Why the curly bracket? [closed]

Why are there the curly braces in the output of DY = {{Cos[ay], 0, Sin[ay]}, {0, 1, 0}, {-Sin[ay], 0, Cos[ay], 0}}; DY // MatrixForm It looks inconsistent ...
1
vote
2answers
91 views
0
votes
1answer
52 views

generation a nested matrix with a partly comparison of two other nested matrices [closed]

(this problem is maybe challenging because of its partly comparison) there are two nested matrices: mainmatrix1: ...
3
votes
3answers
217 views
3
votes
1answer
145 views

How to speed up filling a matrix as much as possible in a loop?

In order to find the solution of an $n\times n$ system of nonlinear equations by the method $x_{k+1}=x_k-D_k^{-1}f(x_k)$ where $D_k$ is an approximation of the Jacobian and defined by \begin{equation}...
0
votes
1answer
48 views

Lift and projection method in Least Squares Inverse Eigenvalue Problems [closed]

I need to implement the lift and projection method proposed by XUZHOU CHEN AND MOODY T. CHU in http://www4.ncsu.edu/~mtchu/Research/Papers/lsiep.pdf on page 7 in ...
2
votes
1answer
123 views

Easier way to calculate Taylor remainder in 2nd order series

At the moment I have implemented the code for a Taylor 2nd order series for the function in three variables: $x_3^3+\frac{x_1-x_2}{x_1+x_2}$ The code builds on following expression: ...
2
votes
1answer
99 views

Product of $N\ 2 \times 2$ matrices and subsequently solving an equation dependent on the product

I have $N\ 2 \times 2$ matrices, each one containing one variable energy which may be complex. I want to muliply them all together to a single matrix ...
1
vote
5answers
179 views

Do not expand matrices in Mathematica calculation

Here is an example of a problem I'm having. Consider that I have defined: omega={{p[t]},{q[t]},{r[t]}} x={{a},{b},{c}} R={{1,2,3},{4,5,6},{7,8,d}} What I would ...
3
votes
2answers
142 views

Chopping matrix elements, real or imaginary

An undesired shape of a matrix has the following form: which is created by ...
3
votes
1answer
72 views
5
votes
1answer
86 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
2
votes
1answer
279 views

Structure analysis based on direct stiffness method. Solve taking too much time

The program generates a very large matrix based on some input from the user. The matrix is symmetric and called generalstifnessmatrix. It also generates 2 other lists(displacement and forces list) ...
2
votes
1answer
83 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). ...
19
votes
3answers
716 views

Why is calling Dot with many arguments so inefficient?

Say I want to multiply a reasonably large list of symbolic matrices. ...
5
votes
4answers
160 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
119 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, ...