Questions on the manipulation of matrices in Mathematica.

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1
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3answers
342 views

Conditional Check on Matrix

Suppose I have the following matrix (i,j): ...
0
votes
0answers
196 views

Back Linear Substitution

I have an equation set Ax=b and A(n*m),n<m . To lower down the dimension, I express some vars by other vars, which gives ...
0
votes
0answers
145 views

eigenvalues and eigenvectors without Root answers

I'd like to find eigen values and vectors of parametric 21*21 Matrix and i cant solve the root problem.please help me to find the answers without Root. My Matrix is: ...
0
votes
2answers
220 views

setting real parameters in Hamiltonian matrix

The following Matrix represents my Hamiltonian. m = {{ B/2 - d - j/2 + a, (Sqrt[2]*j)/2, M}, {(Sqrt[2]*j)/2, B/2 + a, 0}, {M, 0, (-3*B)/2 - d + j/2 + a} How can ...
0
votes
1answer
189 views

Why Eigenvalues thinks matrices are non-numerical

I use Mathematica version 9.0.1. ...
3
votes
2answers
146 views

How do we make a negative integer out of a string of a negative number and vice-versa?

Negative numbers are not taken into consideration by mathematica's built-in functions. FromDigits["-2"] Gives me this message: ...
5
votes
3answers
288 views

Question about Map and Total

Suppose I have a list and I want to generate a new list, such that $$ NewList[index] = \sum_{index \neq j}^{NumOfElts} \frac {1}{ \lvert OldList[index]-OldList[j] \rvert ^2 } $$ Can I do it using ...
0
votes
1answer
84 views

Produce a 1-dimensional list of all unique matrix elements

We have some symbolic matrix m, e.g. m={{1, x, 4 x + y},{0, x y + 4x, 4x},{7 x, x, 4x + x y}} and we want to produce as output a list of all the unique elements ...
0
votes
1answer
451 views

Extracting coefficients from multiple equations and generating coefficient matrix

after 6 hours reading about string patterns, string manipulations and trying ..and trying..I officially give up (for now) and ask for some help. I have some unorderly equations you will find here ...
0
votes
2answers
141 views

How to display output as symbols?

I have this piece of code which populates a matrix following different rules depending on row and column number: ...
0
votes
1answer
62 views

Function output of two lists are only diagonal elements

I'm having a little crysis over here. What I basically want to do is some sort of 3D-Plot, but I'm only interested in the resulting values. I have two vectors x and p: ...
0
votes
2answers
282 views

Define a function on a parameter argument set to zero

Say I have an expression (matrix) that depends on several variables. f= {{a, b+c},{2a-b^2,c^5+a b}} I want to define new matrices with the single parameter ...
4
votes
1answer
202 views

Exported animated gif with matrices will not work?

I want to export a list of matrices as a gif so that they will appear one after another 2 seconds apart. I've tried the following but when I open it up it only does the first two matrices and I have ...
9
votes
7answers
2k views

How to select all elements above the main diagonal of matrix?

How to select all elements above the main diagonal of matrix? I need to create a list of them.
0
votes
1answer
663 views

Symbolic matrix simplification and solving

I am trying to expand or solve an equation that contains matrices for a certain matrix, but it is not working: ...
0
votes
1answer
220 views
0
votes
0answers
121 views

How do I interpret the Roots syntax when I am finding the eigenvalues of a matrix [duplicate]

Here is an example of my problem: I am somewhat confused by the syntax of this. I am guessing that the #1 is specifying the start of another root? Why then does one of the roots = u + with nothing ...
0
votes
1answer
163 views

Applying a general formula

We are a group of students who are struggling with transforming this formula to run in mathematica. In fact there are many formulas that we are struggling with, but if we are able to see how this is ...
0
votes
1answer
138 views

How to faster map density matrix element to make differential equations

I have a time dependent matrix $M(t)$ of $L^n \times L^n$ size and want to write differential equations like D[M[i,j][t],t] = H[i,j][t] Here is my code: ...
-2
votes
1answer
103 views

I need to calculate sin[x] series summation for sin[A] where A is a 3X3 matrix [closed]

I am evaluating $\sin(A)$ where $A$ is a $3\times 3$ matrix. I have calculated it but now I want to check this with a Taylor series expansion of Sin[x]. What I am ...
5
votes
0answers
234 views

Discriminant of Characteristic Polynomial

I'm doing a calculation which finds the characteristic polynomial of a matrix with rather complex entries and then determines the discriminant of that polynomial. For smaller matrices up to around 7x7 ...
11
votes
3answers
2k views

Has Mathematica a function to compute the Smith Normal Form?

The Smith normal form is a matrix that can be calculated for any matrix (not necessarily square) with integer entries. See Wikipedia for a more elaborate description. Has Mathematica a function to ...
6
votes
1answer
527 views

Is there any faster way than Eigensystem to diagonalize a Hermitian matrix?

Is there any faster way than using Eigensystem to diagonalize (get all the eigenvectors and eigenvalues) of a Hermitian (self-adjoint) matrix? That would be ...
1
vote
1answer
144 views

How to place a matrix under controls (sliders) in a Manipulate?

I want to know how I can place a matrix under my sliders. Here is my code: ...
6
votes
4answers
631 views

Counting adjacent elements in a Matrix?

To start, I have a situation where I have some matrix, for example $$ A=\left[ \begin{matrix} 4&2&2&3&3\\ 2&3&1&2&3\\ 3&0&4&0&4\\ ...
0
votes
1answer
139 views

Solving symbolic matrix equation

I have this equation, $$f(x)=Ax-diag(x)(Ax+b)$$, where $x\in \mathbb{R}^n$, $A\in \mathbb{R}^{n\times n}$ and $b\in \mathbb{R}^n$, for which I need to find the zeros. $x=0$ is an obvious solution, ...
0
votes
1answer
281 views

Symbolic Jacobian computation

I have an equation for which I would like to compute the Jacobian symbolically. $$f(x)=Ax-diag(x)(Ax+b)$$, where $x\in \mathbb{R}^n$, $A\in \mathbb{R}^{n\times n}$ and $b\in \mathbb{R}^n$. I am new ...
2
votes
2answers
374 views

Fast randomization of a graph, while keeping the graph connected

I'm looking for a very efficient method for randomizing graph of a given size (N nodes, L links), but keeping them connected. Assume you have the adjacency matrix A of a given connected graph. You ...
1
vote
0answers
354 views

How to extract connected bipartite graph from incidence matrix

I'm trying to extract a connected bipartite graph Bconn from the a given incidence matrix B- I have a matrix representing a bipartite graph - the incidence matrix B (weighted or not is unimportant). ...
9
votes
4answers
4k views

Matrix Multiplication in context of row and column vectors

I've been looking at some matrices in Mathematica and I've noticed something very weird: They're extremely temperamental when it comes to dot products! For example, if I have the following, ...
1
vote
2answers
263 views

How to create automatically some matrices for symbolic manipulation?

I want to create in an automatic way some matrices to do symbolic calculations with them. They look like these: $$ \left( \begin{array}{cccc} a & 0 & b & 0 \\ 0 & 1 & 0 & 0 ...
10
votes
3answers
674 views

How can I complete a correlation matrix with missing values?

I would like to complete a correlation matrix with missing entries, such that the resulting matrix is positive semi-definite. Say I want to find some x and some y in the next matrix that satisfy ...
0
votes
2answers
2k views

Defining a function in terms of matrix elements [on hold]

Currently trying to use elements from a matrix in defining a function however having some trouble. This is a somewhat simplified version of the problem. Say I have the matrix ...
1
vote
1answer
355 views

How Manipulating a matrix and a graphic in only one Manipulate? [closed]

I have to manipulate a matrix and graphics in one big Manipulate-Block. This way: Manipulate[Matrixform[mat],Graphics3D[]] How can I achieve that? Ok, here my ...
1
vote
4answers
182 views

Efficient replacement of conditional nested Do over elements of a matrix

I have two matrices like these: m1=Table[Random[],{i,10},{j,10}] m2=Table[Random[],{i,10},{j,10}] I want to create a new matrix in which its main diagonal ...
10
votes
3answers
608 views

Zero-dimensional matrices

In a recent Mathematica project, $(n \times 0)$- and $(0 \times n)$-dimensional matrices have suddenly become a frustratingly common edge case for me. For instance, consider the following two ...
0
votes
1answer
138 views

Summation matrix

I have problem with summation when it is in matrices. I want to make mathematica compute this: Large X I have added dataset for as well as e. Would anyone be able to show me how to compute this in ...
1
vote
2answers
285 views

How to sort Table/Matrix including legend(Labellings)

I want to sort table including its legend for graph I have table similar to M1 M2 M3 1 5 2 3 1 4 4 2 -10 5 7 11 6 -2 1 ...
1
vote
0answers
260 views

Efficient submatrix swaps for large sparse matrix

I am implementing the 'swap' algorithm for a binary matrix to generate matrix permutations that maintain row and column totals. My problem is that my matrices are large and sparse (e.g., 19774 x 942, ...
2
votes
1answer
148 views

Decomposing a diagonal positive real matrix

I would like to 'decompose' a diagonal positive real matrix $E$ of rank $D$ onto $\sum_{i=1}^{D}c(i)N^i$: $$E = \left( \begin{array}{ccc} 0 & & & \\ & a & & \\ ...
3
votes
2answers
204 views

Select elements of a Matrix that are the same (or have certain relationship) and return their position and the element itself

I have a matrix and I want to pick the elements that are the same and return their positions and their values. It seems easy to me, but all I know is how to pick elements that satisfy certain ...
13
votes
6answers
743 views

Elegantly split a matrix into positive and negative parts?

I have a matrix $M$ of real components, and I want to split it into two matrices $M^+$ and $M^-$ of the same dimensions as $M$, where $M^+$ contains the positive components of $M$ (the remaining ...
2
votes
1answer
1k views

Calculate mean square displacements for different particles from a excel file

I have the particle movement data in the following format: ...
1
vote
1answer
176 views

Transform list of inequalities into matrix form $A\ x \leq b$

I have a list of linear inequalities, and I want to get it into the form $A\ x \leq b$; i.e., find the matrix $A$ and the vector $b$. Is there any function in Mathematica that can that can do this?
0
votes
3answers
243 views

Determinant of a random matrix consisting of integers

I am trying to implement a function that finds the determinant of a random matrix consisting of integers. This is the code I have written so far, but I am stuck. Suggestions ? I want to find a ...
1
vote
1answer
90 views

Multilpe matrix (mxm) and vector (n), wich are unequal, so get a (three dimensional matrix) mxmxn matrix

For example I have this matrix: mk = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}} and I'd like it to multiple with this: ...
1
vote
2answers
415 views

What's the best way to generate all the upper triangular matrix whose singular values are given?

For example, given $\lambda_1 = 1, \lambda_2 = 2, \lambda_3 = 3$, what's the best way to generate all the upper triangular matrix ($3\times 3$) whose singular values are $\lambda_i$? Note:Given a ...
0
votes
1answer
218 views

How to speed up the computation of a specific array

I am doing some calculations on superconductivity and I REALLY need to speed up the way I calculate one of my arrays. I will put the input to the matrix (of course a tiny toy model of what I am ...
4
votes
3answers
428 views

Approximate minimum degree permutation algorithm in Mathematica

In MATLAB there is a nice implementation of the so called AMD (approximate minimum degree permutation) algorithm named amd (see Online MATLAB Documentation). There is an alternative algorithm called ...