Questions on the manipulation of matrices in Mathematica.

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2answers
127 views

Generic Matrices

A multivariate Gaussian distribution for $k$ dimensions looks like this: $$\frac{1}{\sqrt{(2\pi)^k|\mathbf \Sigma|}}\mathbf e^{ -\frac 1 2 \mathbf x^T \mathbf \Sigma^{-1}\mathbf x }$$ $\mathbf x$ ...
1
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1answer
83 views

Checkbox Matrix

Is it possible to create a dynamically changing binary $n \times n$ matrix $A$, which appears to the user as a $n \times n$ matrix/table of checkboxes and the user can change the entries of $A$ by ...
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2answers
65 views

solving series of matrices by simply multiplication

I have a number of matrices {2*2} containing element in series ....so by what method I solve that ... ...
6
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2answers
193 views

How to get rid of nested matrices

If I type into Mathematica TensorProduct[IdentityMatrix[2],IdentityMatrix[2]] It gives me a result that has nested matrices. How do I turn that into a normal ...
2
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3answers
174 views

How can I reproduce the MatrixForm, NumberForm, XyzForm behavior?

I wish to write a function like MatrixForm, that affect only display but not evaluation, i.e. a function that automatically is stripped away from output. More ...
1
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1answer
63 views

references in a nested matrix

I have a nested matrix n: ...
15
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11answers
1k views

Efficient way to build a certain quadratic matrix

For odd n I'm looking for a short and swift way to construct with (f.e.) n = 3 n = 11 ...
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2answers
98 views

Output of mathematica. Quaternion to Matrix

If I have the following instructions: How will it be the output/how will it appears in Mathematica? something like this: I can't recognize the output in mathematica... How can I do to appear ...
5
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0answers
64 views

Bug in PositiveDefiniteMatrixQ?

This seems like a bug in PositiveDefiniteMatrixQ to me: ...
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0answers
75 views

How to sequentially select, from a large set of tuples (of matrices), those with a certain property

I'm interested in finding a computationally efficient way for selecting all tuples of matrices which have a certain property. The property I'm interested in is that I want the column sum, of f[the ...
5
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2answers
99 views

Comparison Operation for Nested Matrices

I have a nested matrix n as bellow ...
0
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1answer
124 views

Rotation matrix $\to$ quaternion

I found a very good link about quaternions in Mathematica , but I don't know how to create a quaternion from a rotation matrix. Can anyone help me, please? Update I need this: A rotation may be ...
4
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6answers
395 views

Insert all elements from one matrix into another

I have two matrices $A$ and $B$ which are the same size. Each element of $A$ is a list of numbers. Each element of $B$ is just a number. How do I insert each element of $B$ into the corresponding list ...
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1answer
78 views

How to power-series expand determinants?

Say $g$ is a matrix which is given as, $g = g_0 + xg_2 + x^2 g_4 .. +x^{d/2 -1}g_{d-2}+ x^{d/2}(g_d + h_d(log (x)))$ where $d$ is an even number and each $g_i$ is a matrix (same dimension as $g$) and ...
0
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1answer
65 views

Matrix operations performed with column-vectors

We have 3 matrices: m1, m2 and b. We want to apply matrix operations (dot or sum) in a ...
1
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2answers
61 views

Importing Text file and removing columns [closed]

I have a file that has 7 column but i only want to import two column from it, that is 1st and 3rd column from the file. How can i do that and this is the list for example: ...
3
votes
2answers
185 views

Addition of Matrices [closed]

How can I add the Matrices created by this: SeedRandom@0; Table[RandomInteger[{0, 34}, {2, 2}], {2}, {5}] // MatrixForm $\left( \begin{array}{ccccc} \left( ...
2
votes
2answers
149 views

Measures of association, Concordant and Discordant

I want to calculate concordant and discordant pairs on nx2 tables. ...
3
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3answers
112 views

Creating nested matrix using random integers

How do i create 15x2 matrix with 2x2 random integer elements? My code only returned identical 2x2 elements:
28
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8answers
2k views

Longest path in 0/1 matrix

I have a matrix of 0's and 1's forming a number of disjoint paths:   I would like to find the lengths of the paths, and from that "spectrum," the longest length (in the above example: 27, ...
0
votes
1answer
118 views

Inverse of a restriction of a non-invertible matrix

Let $A∈R^{4×4}$ be a non-invertible matrix, with $2$-dimensional kernel. How can I compute the inverse of the restriction of $A$ on a subspace where it is invertible: $A^{-1}v \,\,\,\,$ where ...
0
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0answers
37 views

how to rewire the minimum number of edges in a disconnected bipartite graph, so to transform it in a connected one

Consider an incidence matrix A for a bipartite graph (Aij=1 if node i of group 1 and node j of group 2 are connected). A is not symmetric. Assume that A is disconnected or only weakly connected, i.e. ...
1
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1answer
97 views

Principal Components - how to obtain linear transformations?

I have a list "xlsf" with 6 columns and 1200 rows for PCA analysis. The PrincipalComponents[xlsf] gives the following: "The principal components of matrix are linear transformations of the original ...
0
votes
1answer
56 views

Extract a smaller matrix from a bigger one [closed]

May be duplicate, but, how it is possible to make a matrix or table of smaller dimensions, from a matrix with bigger dimensions. I mean, one may want to extract a 25*25 table from a 25*50 matrix. I ...
0
votes
0answers
134 views

3D isosurface plotting

I have a matrix of data of the form of 3 vectors R, Z, M1, M2, M3 ..., cylindric coordinates representing a measurement M of an axisymmetric hypersonic flow at the position R, Z (I don't measure along ...
1
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2answers
113 views

Selecting parts of a matrix via indices given by a vector

I have a column vector of the form $\{1, 1, 2, 3, 2, 3\}^t$ and an associated matrix that has the same number of rows as the column vector, $6$, and a number of columns that is equal to the maximum of ...
3
votes
3answers
203 views

Algorithm to generate a certain matrix

I am looking for a convenient way to generate a matrix of the following symmetric form (numbers could also run from -3 to +3 or just from -1 to +1): Tips, anybody?
1
vote
1answer
110 views

Check every list element for appearance

I'm used to MATLAB so this might be a stupid question but Mathematica is freaking me out. I have a big matrix with the following format: ...
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2answers
107 views
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0answers
49 views

How to find a scaling parameter in matrix inversion process by MMA?

I simply would like to find the inverse of a given matrix $A$ by the iterative method $X_{k+1}=X_k(2I-AX_k)$ using $X_0=\frac{1}{\sigma_{max}^2}A^*$. An example is as follows ...
6
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3answers
161 views

Finding the position of similar elements in a matrix

I want to find the position of the elements which are equal in a matrix. For example in the case of the following matrix: $m =\left( \begin{array}{cc} a & x \\ x & a \\ \end{array} \right)$ ...
1
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2answers
88 views

How to binarize a matrix [closed]

I have this matrix A = {{17/25, 3/25, 5/25, 0, 0}, {5/18, 5/18, 7/18,1/18, 0}, {4/21, 9/21, 4/21, 0, 4/21}, {0, 0, 3/4, 1/4, 0}, {3/4,1/4, 0, 0, 0}} And i ...
0
votes
1answer
52 views

Transition matrix of order n [closed]

I am doing a work about Markov Chains and I have as task to determine, either by induction or by spectral methods, the form of the higher order transition matrix of the model. My transition matrix ...
7
votes
4answers
380 views

Generating an Ulam spiral

An Ulam Spiral is quite an interesting construction, revealing unexpected features in the distribution of primes. Here is a related topic with one answer by Pinguin Dirk, who has provided one ...
13
votes
5answers
451 views

Graph from binary matrix (not adjacency) respecting the original matrix positions

I have a binary matrix. My objective is to connect every close (without "jump") elements with value equal to 1, but I must keep the point positions, just like it's shown at the image. Can somebody ...
2
votes
2answers
105 views

Create a matrix of matrices using Band and ArrayFlatten [duplicate]

I can easily write a simple Band matrix using: SparseArray[{Band[{2, 1}] -> a}, {Dim, Dim}] where a is a number. Now, I ...
0
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1answer
39 views

Matrix as a function of $x$ [closed]

I need to use four functions of $x$ DD11 = @(x) x+0*x; DD12 = @(x) x^2+0*x; DD21 = @(x) cos(x)+0*x; DD22 = @(x) 1+0*x; and since they all represent the same ...
1
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2answers
119 views

dropping a row with at least one value larger than a particular value

So for instance I have M X N table. I want to drop any row which has an element larger than, say, one in the second or the third column. I guess I have to do some sort of pattern matching. But not ...
2
votes
1answer
45 views

Complement for a Matrix

In a matrix, there are some non-zero elements same as: aA= Also, there is a list such as: list = {a, b, c, d, e, f, g, ii, jj, kk}; I want to access to ...
4
votes
3answers
377 views

Efficient matrix / array generation

What is the most efficient way of generating the following matrix? $\left( \begin{array}{ccccc} 1 & 0 & 1 & 0 & 1 & 0 & 1 & \dots\\ \frac{1}{2} & \frac{1}{2} & 0 ...
1
vote
1answer
101 views

Matrix/tensor addition behaving funny under replacement?

I have two matrices I want to add, and one of the matrices is a tensor product of two vectors. I've used a SetDelayed to define the summed matrix, because I want to evaluate it for different values of ...
0
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2answers
135 views
0
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1answer
44 views

Importing a Matrix whit different column numbers depending on the row

I have a bunch of coordinates given in a file. The file contains Startpoints and Endpoints of arrows in columns(Example): ...
3
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6answers
318 views

How can I construct a distance table?

I have a list of city names (of arbitrary length), f.e. c = {"BAL", "NYC", "LAS", "AUS"}; and the distances between them : ...
1
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3answers
123 views

Working with nested matrices

I have a matrix: A = {{a, b}, {c, d}} But each its element, itself, is another matrix too. ...
0
votes
1answer
64 views

Swapping rows and columns in matrix [closed]

If I have an array like the following $\left( \begin{array}{ccc} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \end{array} \right)$ How can I swap the rows and columns, so it is ...
1
vote
1answer
116 views

Matrix and random, weighted assignment of rows

I asked a question in this category previously but my problem has changed. On one hand, I have a large number of data files as .dat format, and on the other hand, I have a matrix ...
1
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1answer
46 views

Correctly substituting a matrix into a scalar equation [duplicate]

I am having trouble correctly substituting a matrix into an (originally) scalar equation. For example: A = {{3, 1}, {1, 2}} cp = CharacteristicPolynomial[A, x] ...
1
vote
1answer
75 views

Calculate the algebraic multiplicity of known eigenvalues of a large, sparse matrix

I have a large (and sparse) matrix with size 1000x1000 -- 10000x10000. I believe i know all eigenvalues for the matrices. All entries are integers and so are the eigenvalues. I want to check this by ...