Questions on the manipulation of matrices in Mathematica.

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3
votes
2answers
123 views

How to convert multidimensional matrix into regular matrix?

I have this multidimensional matrix: {{{{a1, a2}, {a3, a4}}, {{b1, b2}, {b3, b4}}}, {{{c1, c2}, {c3, c4}}, {{d1, d2}, {d3, d4}}}} I would like to convert it into ...
0
votes
0answers
141 views

Speeding up inversion of symbolic matrices by invoking caching

Is it possible to reduce the computation time taken to find inverse of symbolic matrices USING CACHING TECHNIQUES accessible (if any)? I am trying to compute inverse of symbolic matrices of size ...
4
votes
1answer
107 views

Computing Smith Normal form of a matrix with mod p coefficients

I would like to compute the Smith Normal form of a matrix with coefficients in GF(p). In particular, I am interested in GF(2). I have used the Smith normal form packages for integer and polynomial ...
10
votes
1answer
201 views

Drop selection of columns from a ragged array

I have an application where I need to drop some arbitrary list of columns from a ragged array (where of course the shortest array rows have at least all the specified columns). E.g., given a ragged ...
10
votes
1answer
174 views

Sporadic bugs in multidimensional SparseArray objects

Udate This SparseArray[] bug is (apparently) fixed on version 10.0 ...
1
vote
1answer
317 views

How to obtain the orthogonal matrix that diagonalize a symmetric matrix [closed]

I have a real symmetric matrix H which is in symbolic form, I need a matrix P that can diagonalize H; also P is orthogonal and its columns are the eigenvectors of H. How can I doing this in ...
9
votes
8answers
342 views

Fast way to get positions of “boxed” array elements?

Given a 2D array (arbitrary numeric / evaluates to numeric elements, simplified for examples, and can be arbitrary dimensions so long as the operation makes sense, I'm working with 2K X 2K in my ...
1
vote
1answer
94 views

Extracting Imported Information

What I want to do is to compare the relationship between the consumption of say beer and wine using scatter plots where each point designates the particular country (preferably named). I have tried to ...
0
votes
2answers
120 views

Replace matrix with conditions

I want to replace the values of 1. in slot under the condition that the year and month in basevalue and ...
0
votes
0answers
42 views

How do you explicitly define Box Operator (D'Alembert operator)? [duplicate]

I wanted to see how one can define a box operator in mathematica? $$ \Box\phi=(-\frac{\partial^{2}}{\partial t^{2}}+\frac{\partial^{2}}{\partial x^{2}}+\frac{\partial^{2}}{\partial ...
1
vote
0answers
73 views

Define inverse for the custom operator

I want to define simple matrix algebra (inspired by the following posts: Block Matrix Algebra with Mathematica ; How to define custom operators ). I assume the funtion ...
1
vote
1answer
290 views

How can you convert a matrix back into a list of lists?

It is very simple in Mathematica to convert a list of lists into a matrix: all you need to do is apply the //MatrixForm function to it and voila. Is it possible ...
0
votes
3answers
137 views

Implementing nested subtotals

Inserting a nested subtotal in a spreadsheet is a facility that Excel performs very well. But if a subset of this facility can be implemented in MMA for a table which needs it the hassle of its ...
1
vote
3answers
373 views

How to expand the size of the matrix automatically?

I have a matrix in 2x2 a ={{x, y}, {z, u}} I want to expand this matrix 3x3 b ={{x, y, y}, {z, u, x}, {z, x, u}} 4x4 ...
2
votes
1answer
616 views

Contracting with Levi-Civita (totally antisymmetric) tensor

I have an array $v_{ijk}$ which is effectively a rank-$3$ tensor with dimensions $3\times3\times3$, and I need to contract it with $e^{ijk}$, i.e. evaluate $v_{ijk} e^{ijk}$ (see Einstein ...
2
votes
3answers
147 views

Join matrix based on conditions

Given the following matrix: ...
1
vote
3answers
163 views

Conditional Check on Matrix

Suppose I have the following matrix (i,j): ...
0
votes
0answers
80 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
55 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
135 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
0answers
23 views

Jacobian matrix formation from polynomial expressions [duplicate]

I want to find the jacobian matrix for 3 polynomial expression with 3 variables.. the polynomial expressions have the degree of 8.how to form it.?
-1
votes
1answer
105 views

Solve set of non linear differential equations [closed]

I have set of differential equations. For example, I took two equations and tried to solve them as below. I am not getting any results. Please help me to figure it out the mistake. And I wonder if I ...
0
votes
1answer
120 views

Why Eigenvalues thinks matrices are non-numerical

I use Mathematica version 9.0.1. ...
3
votes
2answers
103 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
274 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
65 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
192 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
120 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
0answers
48 views

Differential curve geometry Frenet Formula [duplicate]

I am using Mathematica for differential geometry studies using Frenet Formulae. The problem is that I need to graph the solution curve r[t]. Suppose the curvature of a curve is k(s) = |s|and the ...
0
votes
1answer
53 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
114 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 ...
6
votes
7answers
1k 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
193 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
0answers
53 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
135 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
99 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
69 views

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

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 ...
4
votes
0answers
126 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 ...
4
votes
2answers
532 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 ...
3
votes
1answer
180 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 amazing :). Thanks.
1
vote
1answer
96 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
280 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
73 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
200 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 ...
1
vote
2answers
203 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
183 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). ...
5
votes
3answers
1k 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
114 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 ...