# Tagged Questions

Questions on the manipulation of matrices in Mathematica.

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 ...
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 ...
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 ...
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 ...
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?
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: ...
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} } ...
164 views

### Simple code to write differential equations in a matrix formulation

Is there a simple code to transform the following differential system equations : ...
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. $H^\dagger=H$) ...
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 ...
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 ...
29 views

### MatrixForm in Mathematica [duplicate]

I wanted to do subtractions between to matrices and I did the following ...
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? ...
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?
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 ...
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 ...
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, ...
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: ...
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 ...
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 ...
116 views

### plotting eigenvalues with devoted level coloring

I am about to plot eigenvalues of a matrix versus varyingj's. ...
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 ...
240 views

### Make a vector of sums of matrix rows

I have a matrix in Mathematica: ...
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".
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 ...
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 $$\mu_2[A]=\lim_{t\downarrow0}\frac{\|I+tA\|_2-1}{t}.$$ Hence, I simply code ...
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 ...
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 ...
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}} } ...
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 ...
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: ...
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 ...
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 ...
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 ...
91 views

### Partial comparison between lists contained in larger matrices [closed]

Please presume we have two nested matrices m1 and m2: ...
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: ...
217 views

### Creating a nested matrix from two lists

I have a matrix and two lists: ...
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 ...
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 ...
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: ...
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 ...
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 ...
142 views

### Chopping matrix elements, real or imaginary

An undesired shape of a matrix has the following form: which is created by ...
72 views

### sorting eigenvectors of a final combined matrix

I have two matrices m1 and m2 as below: ...
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
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) ...
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). ...
716 views

### Why is calling Dot with many arguments so inefficient?

Say I want to multiply a reasonably large list of symbolic matrices. ...