Tagged Questions

Questions on the manipulation of matrices in Mathematica.

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How to speed up the construction of a large matrix

As a part of a physics problem that I'm working on, I need to construct a rather large matrix. The matrix is a real symmetric $2^{m}\times 2^{m}$ matrix for some integer $m$, which we would like to ...
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Perform matrix/tensor contractions more efficiently

Problem: explicit index contractions for matrices using the Sum command take too long, and I want to improve the performance for complicated computations. Let me ...
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problem in solving equation

this happened to me when I try to get (f) which should equal sqrt(3)/2 is there any problem in my formula or what? ...
85 views

Plotting eigenvalues smoothly

I am trying to plot how the eigenvalues of a matrix change by changing a given a parameter t. Of course the ordering of the eigenvalues does not matter mathematically but it does when I want to make ...
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Creating a transformation matrix with respect to given bases? [closed]

Let's say I have a linear transformation $T:V\to W$, along with some bases $\{v_1,v_2\}$ and $\{w_1,w_2,w_3\}$ of each respectively. Let's say all the information I have about the transformation and ...
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Efficiently Invert a Square, Block Diagonal Matrix

I am generating an n x n matrix where n is specified by DIM: ...
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Extending matrix (x,y-axis + data) via Interpolation. Looking for elegant & efficient way to write

Please, feel free to edit the title, if necessary. Hi, this is my code working, but actually, the size of my real dataset is 100x100. So, this is very inefficient way. What would be the most ...
147 views

How can I assign matrix values in below form? [closed]

I want to create matrix as the below fig. shows. How can I do it with a do-loop, for-loop, if-loop, or any other way? Thanks a lot...
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Replacing negative components of a matrix with zeros [closed]

How can I replace the negative components of a matrix with zeros?
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Finding the percent difference between elements of a matrix and a list/vector [duplicate]

I have a large matrix of 24 columns, 11 rows, and a vector in the form of a one column, 11 row table. What would be the best method of finding the percent difference between each element of the matrix ...
156 views

Non-rectangular pick of elements of a matrix

How to pick elements of a matrix that are inside a circle centered at the center of the matrix?
154 views

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Creating a tensor from matrices

I have 3 nxn matrices that I'd like to combine into a nxnx3 tensor. Basically, I want a new nxn matrix where each element is a 3 tuple of the elements of the other 3 matrices at that same position. ...
111 views

Matrix Diagonalization programming

I have a very simple problem, with me misunderstanding the use of Modules and Functions in general, in mathematica. I have a function of which I want to input a Matrix, and in the function I want ...
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Percent Difference between elements from 2 matrices

If i have a 22 by 25 table of values which depend on n and r, and a list of values that depends on r that is a 22 by 1 matrix, how can I find the percent difference between each element, by row in the ...
62 views

Plotting plane from a matrix or data table

After weeks collecting data I've decided to pass my results through Wolfram Alpha and see what it gets. The results are amazingly useful, specially the plane generated by linear regression. It is ...
160 views

Zigzag ordered encoding of DCT co-efficients

I am doing DCT steganography. I have obtained a matrix of DCT co-efficient. I now want to perform zig-zag ordered encoding. The matrix is as follows ...
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How to force Series[] to compute expansions by considering non commutative multiplication?

I wish to compute the Taylor series expansion of the following iteration method $x_{k+1}=x_k-f'(x_k)^{-1}f(x_k)$ up to four terms of error ($e_k=x_k-\alpha$). When this is a scalar iteration, I very ...
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Plotting results of 'Do' loop in contour graph

I want to plot the results of a 'do' loop as a contour graph: ...
154 views

How can I optimize the search between two lists, one that is changing length?

I'm trying to identify unique arrays by comparing two lists, one which is growing in length. The number of elements in the list grows as 2^n^2, where ...
138 views

Issue in Det[…] when computing determinants of polynomials?

When I form a matrix of at least size $12 \times 12$ of second order polynomials in $w$ and I calculate the determinant of that, I get something that is a rational expression in $w$. Since the ...
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Plot values of an $m\times n$ matrix on the complex plane with color varying along $m$

Let's say I have a complex valued matrix $\begin{pmatrix}1+I&2+2I&3+3I\\4+4I&5+5I&6+6I\end{pmatrix}$ represented by a list: ...
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How to create overlapped block matrices and simplify the result

This is sort of a duplicate of Creating overlapped block matrices, but the question wasn't fully answered since the OP never returned to clarify. I am using Kuba's answer for FEM, but I have been ...
59 views

Make Function from matrix [closed]

I have a set of excel data (time v temperature). When I extract it to mathematica it creates a matrix. I want to put the temperatures into a function that is time dependent, so is there a way to use ...
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Find the generators and group description of a set of matrices [closed]

I have the following matrix elements: ...
149 views

Repeated multiplication of a square matrix and a column vector in Mathematica

I am very new to Mathematica and StackExchange, so pardon me if I am repeating a question that has already been answered. I am trying to use Mathematica to do the following: u[n+1] = A.u[n] where A is ...
My matrix is $\qquad A= \begin{pmatrix} {1} & {2} & {3}\\ {4} & {1} & {0}\\ {0} & {5} & {4} \end{pmatrix}$ I need $\qquad A^n$ I tried ...