Questions on the manipulation of matrices in Mathematica.

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3
votes
1answer
57 views
1
vote
1answer
60 views

What's is the restrictions for the function MatrixExp?

When I use the MatrixExp on a general $2\times2$ matrix, Mathematica gives me this result: MatrixExp[{{a,b},{c,d}}] // TraditionalForm ...
5
votes
1answer
68 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
240 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
60 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). ...
18
votes
3answers
690 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
135 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
92 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, ...
6
votes
1answer
116 views

List consisting of positions of the matrix elements and the elements themselves

Given a 2D matrix I would like to make a list with elements consisting of positions of the matrix elements and the elements themselves. Let the matrix be ...
4
votes
1answer
90 views

How to increase the evaluation speed of this somewhat complicated table / matrix operation?

I'd like to calculate the following one-dimensional array: OneDimArray = Table[(Norm[Sum[ MatrixA[[i,j]]VectorB[[j]],{j,N}]])^2,{i,N}] However this takes a very ...
2
votes
1answer
129 views

different situations with Compilation of ConstantArray

First, we load some tools related to Compile for analysis. ...
1
vote
2answers
61 views

How to replace the selected value in matrix with a specific digit?

I want to replace the selected values through "RandomChoice" by 1 and all other values in matrix with 0. I want output in binary form matirx. ...
2
votes
0answers
35 views

Real Canonical Form of Arbitrary Size Matrices

I have been searching the site and the Mathematica documentation, but have not found anything regarding this. If we find the Jordan Form of the following matrix, we get complex values, but I would ...
3
votes
2answers
112 views

Factor multiplied matrix with vector

Say I have a matrix multiplication of the form $$B=A\cdot X$$ or $$\left( \begin{array}{c} \text{a11} \text{x1}+\text{a12} \text{x2}+\text{a13} \text{x3} \\ \text{a21} \text{x1}+\text{a22} ...
0
votes
0answers
68 views

What is the function in Mathematica that can be used to find the derivative of a constant value function with respect to an arbitrary matrix?

I have a function that consists of some matrices. This function results in a constant value. I need to take the partial derivative of this function with respect to one of the matrices it depends on. ...
23
votes
5answers
882 views

Can (compiled) matrix permanent evaluation be further sped-up?

Update III  Mathematica 10.2.0 now ships with a predefined System`Permanent function, which the PermanentCode package ...
2
votes
1answer
70 views

Eigenvectors choose intuitive ordering/sorting

Starting from some symmetric $L\times L$ matrices $M$(see below), I want to compute the eigenvectors in Mathematica, in order to construct an ...
5
votes
3answers
942 views

Generating random symmetric matrix

Suppose first that I want to generate a matrix whose elements are independent and identically distributed (i.i.d.) with distribution dist. This is easy: ...
0
votes
2answers
96 views

How to map the second highest value in each row of a matrix

I have a matrix with three or more columns called mat. I would like to map the second highest value in each row of mat into its ...
13
votes
2answers
449 views

more numerically accurate inverse matrix

I encountered the following matrix mat = {{2, 2.161209223472559` + 1.682941969615793` I}, {2.161209223472559` - 1.682941969615793` I, 2}} and ...
1
vote
2answers
127 views

LUDecomposition for non-square matrices

How do we go about finding the LUDecomposition for non-square matrices. When i try to input the standard LUDecomposition ...
1
vote
2answers
117 views

How to parallelize this code?

Initialize a matrix a with value of $\alpha$ in central cell as "ice", and $\beta$ in every other cell. ...
1
vote
0answers
29 views

Fast arithmetic on matrix elements

I have a square matrix $U$ of dimension $L\times L$, I am interested in the following quantity $U_{1,j}U_{2,k}U_{3,l}U_{4,m}\cdots U_{L,q}$ summed over all permutations of the letter indices, ...
1
vote
4answers
325 views

Create a Pascal Matrix

I am trying to write a function that can create a Pascal matrix. So far I have ...
3
votes
1answer
49 views

How to fill a tensor with matrices one by one?

I have this tensor: nn = 4; tableToFill = Table[x, {p, 1, nn}, {q, 1, nn}, {i, 1, nn}, {j, 1, nn}]; that I want to fill with a matrix one by one with a matrix ...
3
votes
0answers
49 views

FindInstance of Matrices

I'm trying to use FindInstance to find examples of matrices that complete an expression. However, it seems like I need to specify atomics as my variables to the function. So, here's a really simple ...
0
votes
0answers
46 views

Can't operate on vector within a list of rules

I'm trying to set up a list of rules which includes the following: ...
0
votes
0answers
47 views

LatticeReduce question

Does LatticeReduce work with arbitrary precision arithmetic? That is, if I give it a linearly independent integer basis, but the integers are 40 decimal digits long ...
7
votes
1answer
219 views

How write a new MatrixRank feature with symbolic computation

The current MatrixRank is a slight foolish without any capacity of symbolic computation ,feature of Mathematica, like this: ...
0
votes
0answers
45 views

How to tweak a symbolic RowReduce?

B = {{-1, 1, 0, a}, {-1, 1, 0, a}, {-1, 1, 0, b}}; MatrixForm[B] RowReduce[B] // MatrixForm Mathematica is indeed giving ...
3
votes
1answer
98 views

FindMaximum “is not a real number at” nrnum problem

I'm experiencing a problem using FindMaximum that I don't understand (due to my newbie knowledge of Mathematica's syntax). That is, FindMaximum sometimes returns a (correct) answer, but sometimes ...
0
votes
1answer
39 views

Tolerance of PositiveSemidefiniteMatrixQ [closed]

I believe the following should be True but returns False for me: ...
0
votes
1answer
55 views

Generate random Hermitian matrices [duplicate]

I want to generate random Hermitian matrices. For now, random Hermitian matrices with size 2 are obvious to construct. But elegant methods for higher dimension would be nice! Are there methods besides ...
0
votes
0answers
34 views

Handling a matrix with components greater than machine precision

I have four quantities stemming from a 4th order differential equation. I can represent these as a vector which is a product of a 4X4 matrix $$ M=\left\{v,\frac{\partial v}{\partial x},\frac{\partial ...
3
votes
3answers
111 views

How can I make custom accumulated sequences like the following?

First of all, I don't really know how to formulate the question, so if you understand my question and know a better way to phrase it, please revise. I have the following Matrixes: ...
2
votes
1answer
413 views

Understanding the difference between matrix indices and image coordinates in context of ListDensityPlot

In Mathematica help it's written that: ListDensityPlot[array] -> generates a smooth density plot from an array of values. ...
2
votes
2answers
68 views

Problem with ArrayFlatten to concatenate matrix

I would like to concatenate 2 matrix : - the first which is a line of 2 elements - the second which is a matrix of 2-2 elements I use the following code : ...
6
votes
2answers
67 views

A problem about matrix/vector extension via $\tt ArrayPad$

Given that I have a vector and matrix as follow: vec = Array[Subscript["P", #] &, 6, 0]; mat = Array[Subscript["P", #1, #2] &, {5, 4}, {0, 0}]; And I ...
2
votes
1answer
55 views

Eigenvalues are not the same in the special case

I have this matrix: h = { {e1, 2, x}, {2, 2, x}, {x, x, 2} }; I want to calculate the eigenvalues and then set x equal to zero: ...
6
votes
1answer
62 views

Matrix Multiplication after “Flatten”

Say we originally had two matrices, $A$ and $B$, both $n \times n$, whose product $$ C= A.B $$ Now I flatten $A$. I can obtain a flatten $C$, from the following multiplication $$ ...
14
votes
5answers
537 views

A quicker than outer

I need to get a matrix $\{a(x_i-x_j)\}$, where $x_i$ form a partition of an interval, $a(x)$ is a given function. I use ...
2
votes
3answers
62 views

How can I create a dynamic Matrix inside a function?

I have a function where a n parameter is handed and a list of values is calculated inside of it. I then need to solve a linear system of equations that require me ...
1
vote
1answer
93 views

Visualizing Matrix that represents a network

I have a nxn matrix $A$ that represents a network. I have $n$ nodes in the network, and the matrix $A$ represents the number of connection (edges) between the different nodes. For example, if $A$=0, ...
3
votes
2answers
263 views

Understanding polyharmonic splines

Rahul Narain and J.M. gives implementation of the thin plate polyharmonic splines in this post. Rahul Narain's method is clear. J.M.'s is convenient to reuse. But J.M. used too many ...
0
votes
1answer
63 views

errors in simple for loops

Im trying to run the following code, which I have translated from Matlab. I created a for loop nested inside another for loop. mW is a matrix, and ...
3
votes
1answer
173 views

how can i associate the headings of columns/rows with content of itself and then recall what i want after i've imported the excel file in mathematica

Hello, i make another try... I have to import a file like this below (it is an excel file, i show you just the beginnig. it should have thousend of rows and columns). After i've imported the file i ...
0
votes
1answer
43 views

Output of Coefficientrules into Jacobian matrix

I have a pair of large polynomials in u, v, a1...a9 and b1...b9, generated by ...
0
votes
2answers
44 views

Enlarge a matrix and fill in zeros [closed]

Suppose I have a dynamically generated 4-dimensional matrix L in the shape shape={d1, d2,d3,d4}, and ...