Questions on the manipulation of matrices in Mathematica.

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2
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1answer
42 views

Extract Transfer Matrix from TransferFunctionModel

I have a MIMO transfer function model, and I'd like to know how to perform arithmetic on this model. For instance, to see the difference between two systems' outputs for arbitrary inputs, I'd like to ...
1
vote
1answer
68 views

Handle matrices and vectors with general dimension

I have a matrix of $n \times n$ dimension: $$ K - \omega^2 M = \begin{pmatrix} 2\omega_0^2 - \omega^2 & - \omega_0^2 & 0 & \cdots & 0 \\ - \omega_0^2 & 2\omega_0^2 - \omega^2 ...
5
votes
3answers
247 views

Huge matrices crashes in Mathematica

I have a matrix of data ~(70,000x70,000). I am searching connection between these data points. I use euclidean distance for that purpose. If it is less than my threshold (that means they have ...
1
vote
0answers
35 views

Diagonal times dense matrix, high precision

I have a fixed dense matrix M of high precision numbers, say 40 by 40 and precision 40. Then I have a variable vector v of the ...
6
votes
3answers
179 views

On a strange pattern of triangular numbers in Ulam's spiral

In this MSE post, user GeMir noticed that, where the green dots are the triangular numbers, $$T_n = \frac{n(n+1)}{2} = 1,3,6,10,15,21,28,36,45,55,66,78,91,105,120,136,\dots$$ in the Ulam spiral ...
15
votes
0answers
200 views

Simple Matrix multiplication takes very long

Bug introduced in 10.1.0 I came across some strange behaviour during a computation involving matrices with symbolic values. It is reproduced below. Multiplying a random 30x30 array with symbolic ...
1
vote
1answer
62 views

Displaying a matrix with integral entries

I have a matrix nxn with coefficients a[i,j] like: a[i,j]=NIntegrate[T[r], {r, -le, le}] - NIntegrate[T[r] Abs[r]/le, {r, -le, le}] I can solve the matrix but I ...
1
vote
0answers
28 views

Function to be used for spectral decompostion of matrix [duplicate]

Can anybody please help in finding out what is best way to do spectral decomposition (or Eigen decomposition) of the matrix. The details of Eigen decomposition can be found in attached link 1. ...
1
vote
0answers
48 views
2
votes
0answers
62 views

MatrixRank of a large but sparse matrix

I want to find the rank of a very sparse, quite rectangular matrix mat, but I'm running out of RAM (I have 16 GB) if I try to use ...
0
votes
0answers
48 views

Compilable function with the functionality of SingularValueList

I'm doing something that involves finding the singular values of a lot of matrices. Basically I need to find singular values of $n$ matrices of dimension $n\times n$, where $n$ is as large as ...
1
vote
1answer
90 views

Matrix multiplication for higher dimensional matrices [duplicate]

I have a matrix like this (myb1): I would like to get the matrix multiplication of each of the submatrix to itself. For example the first 2x2 matrix $\begin{bmatrix}1 & 2\\1 & ...
1
vote
1answer
64 views

Multiplying three matrices does not give expected form [closed]

I'm having lectures on analytic geometry. I've learned that there is an associated matrix multiplication for a quadratic form: $\quad \quad \left( \begin{array}{ccc} x & y & 1 \\ \end{array} ...
3
votes
1answer
81 views

Eigenvalues function not producing expected results?

I'm running into a strange issue when trying to compute eigenvalues of a 2x2 matrix for graphene. If I "manually diagonalise" by multiplying the two off-diagonal terms together and taking the square ...
2
votes
0answers
32 views

How to get simultaneous eigenvectors of commuting matrices? [duplicate]

So let's say there are two square matrices A and B that commute (AB-BA=0). This implies that there must exist some complete set of vectors that are eigenvectors of both A and B. Is there any way to ...
0
votes
2answers
34 views

How to get Complement function working in a For loop? [closed]

I've been working on a piece of code that will delete small components from a nested uneven matrix (n pages, n rows, 3 columns), by deleting the pages with less than ~30 rows. However, I've notice ...
1
vote
1answer
36 views

Can I rely on the ordering of the adjacency matrix? [closed]

Suppose I have created a Graph[{1,2..n}, {1->3, etc}], and I take the adjacency matrix of that graph. Can I rely on the fact that the i-th entry in the graph is the i-th node in the matrix? Or maybe ...
1
vote
0answers
45 views

Does a matrix need to be rationalized when calculating MatrixExp? [closed]

I have a sparse matrix, L, and need to calculate its exponential, MatrixExp[L t], where t is ...
1
vote
2answers
161 views

Having trouble translating Matlab `fsolve` into Mathematica

I searched the site and found that someone said FindRoot is equivalent to fsolve, however, without proper options, ...
3
votes
3answers
168 views

Matrix with known entries but unknown size [closed]

I am trying to perform some calculations with a matrix that has let's say size N but unknown, please How can I write this in mathematica?
3
votes
1answer
86 views

How to tell Mathematica that my variable is a scalar

In my calculations I have these combinations PauliMatrix[1].f PauliMatrix[2] where f is a scalar function. The result is as ...
4
votes
3answers
161 views

How to produce a matrix plot from 3 matrices a, b and c following RGBColor[a[[i,j]],b[[i,j]],c[[i,j]]]?

I am trying to produce a single-plot from 3 matrices, let's say: ...
0
votes
1answer
65 views

How does one initialize large arrays in Mathematica with a structured format? [closed]

I want to create a 10 by 10 matrix that increases by 1 every unit across like: 1 2 3 4 5 6 7 8 9 10 11..... Is there a function that does this without having ...
7
votes
1answer
109 views

Challenging matrix sorting request?

I have an application in mind, and I need to do the following analysis, but am having a high degree of difficulty conceptualizing it in terms of syntax. I understand what I want, but cannot seem to ...
2
votes
1answer
125 views

Mathematica error code 0x00000171

I'm getting above error code with a Trap 132 indication when attempting an ArrayPlot of a complex 130000 x 2048 matrix. Using Mathematica 9.0.1 with Mac OS 10.10.3 ...
3
votes
1answer
78 views

Extracting a time series from a sound object

After importing a sound file, how can I generate a time series (preferably as an $n\times 1$ matrix) which gives the intensity at equal time intervals?
1
vote
1answer
93 views

Unexpected inefficiency when calculating matrix product by Dot

There is an unexpected inefficiency when I calculate matrix product by Dot. The only relevant part of my code is presented as follows: ...
0
votes
0answers
54 views

Null space of a stochastic matrix [closed]

I want to calculate NullSpace of a matrix m - IdentityMatrix[n]. Normally I would do it with ...
4
votes
2answers
120 views

Pauli matrices — simplify expressions without printing out the raw matrix

Squaring a Pauli matrix results in the identity matrix. These bits of documentation (weakly, to a Mathematica-newbie like me) imply that some algebraic identities that link the Pauli matrices ...
0
votes
0answers
34 views

Why is there a different eigenvector for the same matrix? [duplicate]

I have a matrix that depends on two variables x and y. Matrix[x,y] When I make x=-.25*(1 - 1/3) + .25*(1/3) + .25 y=0 I ...
12
votes
1answer
293 views

How do I create a triangulated surface from points?

I have a set of points in a nx3 matrix and I would like to convert them into a surface, so that I may calculate its surface area. The function ListSurfacePlot3D creates the surface how I want it. ...
3
votes
2answers
136 views

Matrix Plot: How to Apply color function to only a region of the plot

I want to make a matrix plot where a color function is applied to a region of a matrix. Those matrix elements which were not in the region specified should not have any color associated with them, and ...
1
vote
1answer
67 views

How to specify positions in a matrix by an array?

If I have an array of sets of points such as pts = {{2,4},{1,3},{5,7}} Is there any super short command to use those pairs to output their respective elements in ...
0
votes
1answer
83 views

How do I store Eigenvalues of a 14*14 matrix in a For loop into an array and then plot that array? [closed]

I have a matrix 14*14 that is dependent on parameter a. How can I plot eigenvalues of the matrix according to varous values of a?
2
votes
5answers
194 views

Add values from a list, at positions from a list, to a matrix

I'm investigating matrix assembly and one of the things I'm trying to do is add specific values to a larger matrix based on a list which is essentially defining connectivity of nodes. For example: ...
0
votes
0answers
41 views
0
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0answers
55 views

Normalized, symbolic Eigenvectors without abs(), sign() etc

I'm trying to compute the normalized eigenvectors of a matrix M = {{0, 0, 0, 0}, {0, 0, M5, 0}, {0, M5, 0, M4}, {0, 0, M4, 0}} If I try Normalize ...
0
votes
0answers
45 views

vector product defined on kronecker delta [duplicate]

I have some vectors such as : a={{0}, {0}, {0}}; b={{1}, {1}, {1}}; c={{1}, {1}, {0}}; I wanted to product a by ...
2
votes
1answer
57 views

formatting matrix

I have imported a matrix from data file which was generated in Matlab. The problem is the character (") in beginning and end of every row. So I can not perform any operation on it. How to get out ...
4
votes
1answer
177 views

Eigenvalues of matrix not giving imaginary parts

This might be a very simple problem, but I can't seem to figure out why I am getting this. I am trying to find the eigenvalues of the matrix: ...
0
votes
0answers
65 views

Operatorial matrix

Suppose I have a matrix M=$\begin{pmatrix} A(p) & B(p) \\ C(p) & D(p)\end{pmatrix}$. I want to apply some operatorial matrix E such that EM=$\begin{pmatrix} 0 & \partial_p & \\ ...
3
votes
1answer
61 views

Recognising degenerate maxima in a matrix

Say I have the following matrix $\left( \begin{array}{cccccc} 1. & 0 & 0 & 0 & 0 & 0 \\ 0 & 0.707107 & 0 & 0 & 0 & 0.707107 \\ 0 & 0.707107 & 0 ...
0
votes
1answer
53 views

Designing a loop that fetches 5 random vectors each with 5 components from a set of 10 until Linear dependence is found

I am currently trying to find a way to make a loop that will select 5 random columns without replacement of a 5x10 matrix until it finds a determinant equal to 0 out of the new matrix formed by the 5 ...
0
votes
1answer
34 views

Problem with writting into a matrix in Mathematica [closed]

I have declared a matrix using S = ConstantArray[0, {246,246}] And when I try to write into it by a loop I get the following error "Tag Times in 0\ Null is ...
2
votes
1answer
86 views
-1
votes
1answer
148 views

Strange bug involving a list, “Objects of unequal length” [closed]

sortedTally is a list generated from Tally sortedTally[[1]][[1]] is a list If I print: ...
0
votes
1answer
64 views

How to count column occurrences in a matrix?

I have a matrix of data, and I want to count the number of columns that match, and have some way to organize them by frequency. But I don't want to count the entire column, but consider the matrix ...
1
vote
1answer
54 views

How to swap tensor indices without permutation?

Say I have a tensor of rank R, How to swap $i^{th}$ and $j^{th}$ tensor index? I do not want to use TensorTranspose because it requires to write down the entire permutation, i.e. ...