# Tagged Questions

Questions on the manipulation of matrices in Mathematica.

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### What is the fastest way to obtain the eigenvalues of a Wishart matrix?

I would like a fast method of creating a sample of random numbers which corresponds to the eigenvalues of a Wishart matrix: For M>N the eigenvalues \lambda_i are given by the jpd Where $K_N$ is ...
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### Hasse Diagrams from Adjacency Matrix

Let's say I have a rather large adjacency matrix for a partial order relation. Say an 80x80 matrix. What is the best way to display Hasse diagram? I have tried AdjacencyGraph and it does a not so bad ...
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### Picking some elements of a matrix and generating another matrix [duplicate]

If we have a nested matrix as: start={ {{1, 2, 2, 3}, {1, 1, -2, 1}, {3, 2, 2, -I}, {1, 2, 0, -I}}, {{3, 4, 4, 0}, {1, 1, 4, 1}, {3, 3, 4, -1}, {1, 1, 2, I}} } ...
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### Factor vector out of a matrix

I am wondering how to factor a[1],a[2],...,a[4] out of sim so that I can write sim as the ...
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### wrong result of an iteration related to replacement and comparing

We have two nested matrix and a code for replacement following an equality as: ...
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### replacement in a nested matrix

We have a nested matrix m1 = {{{1, 2, 2, I}, {1, 1, -2, 1}, {3, 2, 2, -I}}, {{3, 4, 4, I}, {1, 1, 4, 1}, {3, 3, 4, -1}}}; we must replace the first number of ...
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### Conditionally binarizing matrices

I want to (fastly) convert matrices with values that are <= a threshold to binary matrices. I used a call to Binarize, but I don't like the Image and ImageData conversions as they obfuscate the ...
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### Why the curly bracket? [closed]

Why are there the curly braces in the output of DY = {{Cos[ay], 0, Sin[ay]}, {0, 1, 0}, {-Sin[ay], 0, Cos[ay], 0}}; DY // MatrixForm It looks inconsistent ...
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### Partial comparison between lists contained in larger matrices [closed]

Please presume we have two nested matrices m1 and m2: ...
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### generation a nested matrix with a partly comparison of two other nested matrices [closed]

(this problem is maybe challenging because of its partly comparison) there are two nested matrices: mainmatrix1: ...
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### Creating a nested matrix from two lists

I have a matrix and two lists: ...
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### How to speed up filling a matrix as much as possible in a loop?

In order to find the solution of an $n\times n$ system of nonlinear equations by the method $x_{k+1}=x_k-D_k^{-1}f(x_k)$ where $D_k$ is an approximation of the Jacobian and defined by ...
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### Lift and projection method in Least Squares Inverse Eigenvalue Problems [closed]

I need to implement the lift and projection method proposed by XUZHOU CHEN AND MOODY T. CHU in http://www4.ncsu.edu/~mtchu/Research/Papers/lsiep.pdf on page 7 in ...
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### Easier way to calculate Taylor remainder in 2nd order series

At the moment I have implemented the code for a Taylor 2nd order series for the function in three variables: $x_3^3+\frac{x_1-x_2}{x_1+x_2}$ The code builds on following expression: ...
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### Product of $N\ 2 \times 2$ matrices and subsequently solving an equation dependent on the product

I have $N\ 2 \times 2$ matrices, each one containing one variable energy which may be complex. I want to muliply them all together to a single matrix ...
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### Do not expand matrices in Mathematica calculation

Here is an example of a problem I'm having. Consider that I have defined: omega={{p[t]},{q[t]},{r[t]}} x={{a},{b},{c}} R={{1,2,3},{4,5,6},{7,8,d}} What I would ...
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### Chopping matrix elements, real or imaginary

An undesired shape of a matrix has the following form: which is created by ...
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### sorting eigenvectors of a final combined matrix

I have two matrices m1 and m2 as below: ...
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### 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
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### 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) ...
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### 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). ...
699 views

### Why is calling Dot with many arguments so inefficient?

Say I want to multiply a reasonably large list of symbolic matrices. ...
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### 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: ...
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### 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, ...
120 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 ...
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### 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 ...
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### different situations with Compilation of ConstantArray

First, we load some tools related to Compile for analysis. ...
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### 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. ...
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### 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: ...
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### 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. ...