Questions on the manipulation of matrices in Mathematica.

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2
votes
3answers
200 views

MatrixForm explanation as why row extract is displayed as a column?

I have a 5 x 5 matrix: cdsSpread5yrs = But after doing a row extract, why is it displaying as a column? ...
9
votes
2answers
767 views

How to transform a 3D image by an affine transformation matrix

I have a question concerning Image Processing: I have a stack of images, which I can compose to a 3D image using Image3D. Additionally I have a 4x4 affine transformation matrix. I would like to ...
0
votes
2answers
356 views

Matrix Plot – Little Exercise

Hi there, mathematicians. I'm not very good at coding plots in Mathematica, so I was hoping that one of you could help me solve a problem I'm having. I have the following matrix plot: ...
4
votes
2answers
535 views

Exact cover solution

Is it possible to get a exact cover solution(s) and/or number of possible solutions in Mathematica?
3
votes
3answers
186 views

Need Help Writing (a Pascal) Matrix in Mathematica

I want to write a function $f[n]$ in Mathematica which gives me an $n\times n$ lower triangular Pascal matrix with a row of zeros in between each nonzero row. That is, I want the matrices ...
9
votes
1answer
251 views

Verifying and deriving basic (block) matrix identities

How can I use the new symbolic matrix/tensor capabilities to verify matrix identities, such as (1) or (2) Even better, how can I ask Mathematica to derive expressions for X, Y, Z, and U like ...
5
votes
2answers
385 views

Sort matrix by columns and rows without changing them

I would like to sort a matrix in descending order first by the total of each column, then by the total of each row, but without changing their content. For example, if I had: ...
1
vote
1answer
314 views

A lot of matrix multiplication

So I have a set of 15 $4\times 4$ matrices which I call $X_i, (i=1,2..15)$ and a set of 6 $4\times 4$ matrices which I call $y_j, (j=1,2...6)$. Now I have to calculate $(X_i y_j)-(y_j X_i^*)$ for ...
6
votes
3answers
687 views

How to manipulate gauge theory in Mathematica?

I want to know if there is a way of typing into Mathematica an expression like the following, $$\epsilon^{\mu \nu \lambda} f^{abc} A^a_\mu A^b_\nu A^c_\lambda + g\epsilon^{\mu \nu \lambda} A^a_\mu ...
3
votes
3answers
220 views

Are table headings functional?

Are table headings for aesthetics only? If I have: ...
7
votes
4answers
192 views

Generating all matrices with 1 (possibly) replaced by -1

I have a matrix $M$, whose dimension I am unsure of, which has only $\lbrace0,1\rbrace$ entries. I would like to generate all the possible matrices that result from changing (some subset) of the $1$'s ...
1
vote
1answer
152 views

Optimization of correlation calculation

How can I make the following line of code run faster? Is there a way to do this calculation as a matrix vs vector than vector vs vector? In the code below, f is a ...
2
votes
1answer
269 views

How to modify a matrix to satisfy a special condition?

I have matrix like this: How do I modify this matrix to make it satisfy the following condition: For each element {i, j} in the matrix the sum of the elements of row i must be equal to the sum ...
4
votes
6answers
236 views

Sorting Matrix elements

I have matrix in as shown, consisting of real numbers and 0. How can I sort it to become out as shown? ...
5
votes
3answers
378 views

How to sum matrix elements based on finding the first (and second) non-zero elements of each row?

I have a matrix: I would like to sum all the first non-zero elements of each row so that I get a value of $$25.5317 + 8.85471 + 6.90018 + 32.9436 + ... $$ and so on and simply ignore zero rows. ...
1
vote
1answer
267 views

How to do conditional matrix division when elements are a combination of zero and real numbers?

I tried to divide two large matrices DLand PL of size 100,000 x 5 each and they look like this, DL= and PL= By using conditional function: ...
0
votes
0answers
35 views

Why isn't the matrix product computed? [duplicate]

Possible Duplicate: Why does MatrixForm affect calculations? I have the following input: Why is the matrix not computed, giving me a $2 \times 2$ matrix?
1
vote
1answer
210 views

How to Sort on row by row basis?

Say I have matrix how to sort on row by row basis to get:
1
vote
2answers
590 views

How to take matrix elements as input to another matrix or loop?

Say I have matrix tmp1 of size 1000 x 5 (shown is just a small section for illustration purpose), consisting of real numbers and 0: How can I iteratively take every non-zero real number elements and ...
2
votes
3answers
335 views
0
votes
1answer
528 views

using Mathematica's matrix multiplication in C++

Is there any way that I can utilize Mathematica's matrix multiplication in a C++ program? I'm making a 3D graphics engine (for class) in C++ and I would really like to use Mathematica for all of my ...
1
vote
1answer
490 views

Matrix Multiplication Modulo 2

I would like to perform matrix multiplication modulo 2. Hence, instead of the usual: A.B I did: ...
0
votes
2answers
231 views

How to do equality check of a large matrix and get the corresponding index position?

Say I have a matrix A = 1000 x 5, and I want to compare it's first element (uppermost top left) to each of the 5 elements in the first column of matrix B of size 5 x 5. Whenever the first time the ...
6
votes
1answer
582 views

vectorial ODE in mathematica with matrix exponentials

I want to solve the following equation in mathematica : DSolve[{X'[t] == A.X[t], X[0] == ( {{0},{0}} )}, X[t], t] It is a system of 2 ODEs coupled by the matrix A, ...
3
votes
0answers
198 views

Mathematica Complains about Non Symmetric Covariance matrix, when it's not the case

I was doing some fitting with Mathematica7 using NonlinearModelFit. It's quite long the program to do the fit and that's why I am not displaying here ... It goes ok, and I can get the fit parameters ...
0
votes
1answer
162 views

how to get modify the following correlation matrix with a specific list of financial prices?

The following takes the last 5 members of the Dow Jones index and plots the correlation matrix of the last 5 years of daily prices: ...
2
votes
1answer
443 views

Tridiagonal matrix for any n

I'm pretty new to Mathematica and I need to figure out how to create a $n\times n$ tridiagonal matrix for any $n$. I don't have the slightest clue where to begin. Edit: got this far, not sure how to ...
2
votes
1answer
255 views

Creating a matrix from the output of a variable inside a for loop

I would like to enter the results of the following loop inside a matrix as its elements: ...
1
vote
0answers
228 views

Can mathematica simplify an expression setting simplified answer equal to zero?

Basically I want to reduce something like: Subscript[P, 4] - Subscript[P, 5] == Subscript[R, 4, 5]* Subscript[i, 4, 5] when only one of them is known (...
1
vote
2answers
653 views

How to calculate FDCT

I'm new to Mathemtica and I'm trying to calculate Discrete Cosine Transformation FDCT. I found the FourierDCT built-in function, but not DCT, so I need to implement it. I have tried couple of ideas ...
1
vote
1answer
528 views

Calculating an exact orthogonal modal matrix in Mathematica

I can calculate the modal matrix of a matrix A using the command JordanDecomposition[A][[1]], and a decimal approximation of the orthogonal (or normalised) modal ...
1
vote
2answers
268 views

How to extract RGB arguments as a list

Although the following lines of code work fine they are very awkward. My questions are below a = RGBColor[1, 0, 0] b = RGBColor[0, 1, 0] Is there a more compact ...
4
votes
1answer
260 views

Printing Block Matrices

I have a 2D matrix, such as: d=2; M=Array[a, {d^2,d^2}]; and I would like to print it in a way which emphasizes its dxd block matrix structure. If ...
6
votes
2answers
1k views

Eigenvalue / Eigenvector Calculation

I'm currently trying to compute the three smallest eigenvectors for a 34 by 34 matrix. While I was expecting this to take some time, Mathematica has been running for the past 3 hours, which seems ...
2
votes
5answers
147 views

Test First row of matrix

What is a good way to test the first row of a Matrix to check if one of the values equal a value. For instance, In this example, I want to get vector in the second row that has the bigger value in the ...
2
votes
2answers
425 views

Total Variation Distance of probability matrix

How can I calculate the Total Variation Distance of a transition Matrix? is there any built in function? I've searched all documentation and haven;t found anything. ** More information: Let me try ...
4
votes
2answers
463 views

Loop and do operations on Matrix, then graph the results

I'm trying to do some operations to a matrix in a loop, and then I want to graph the results. The results are pair of numbers. Can I store the results of each iteration on "something" and the use ...
4
votes
2answers
239 views

Transform x-scale of data for e.g. MatrixPlot

I have to transform in a nonlinear way the x-scale of some data for a MatrixPlot (or ReliefImage or ...
2
votes
1answer
189 views

Numerical comparisons of matrices

I have a matrix which should be equal to a null matrix. However due to the numerical precision, a brutal equality test with a matrix initialized with zeros does not work. How should I perform the ...
3
votes
1answer
693 views

stationary distribution of a transition matrix

How can I solve the stationary distribution of a finite Markov Chain? In other words, how can I estimate the eigenvectors of a transition matrix?
5
votes
1answer
1k views

Mathematica won't give eigenvectors but Wolfram Alpha will? What am I doing wrong?

If I ask Mathematica to find the eigenvectors and eigenvalues of the matrix: ...
2
votes
1answer
1k views

Creating a random normal matrix

I would like to create a random matrix with the constraint that the matrix must be normal, i.e. the matrix and its Hermitian conjugate must commute. I would create a random matrix "without ...
12
votes
4answers
317 views

Inputting a big structured matrix in Mathematica

Hi this is my first post and this is a problem that has bothered me a lot. Suppose we have the $2012\times2012$ square matrix: ...
12
votes
1answer
445 views

How to extract and replace submatrix of a doubly-periodic matrix?

How can I effectively extract and replace a rectangular subpart of a toroidal matrix, i.e. one where boundaries are connected at opposite ends? Since the submatrix can overhang the edges, a simple ...
2
votes
3answers
717 views

Finding eigenvalues of a $1500\times1500$ matrix

I need to find the eigenvalues of a $1500\times1500$ real symmetric matrix given by $A_{i,i+1}= A_{i+1,i}=-1$ and also $A_{1,N=1500}=-1$ (this is because of a periodic boundary condition used) and all ...
4
votes
4answers
2k views

How to convert equation to vector (matrix) form?

How can I convert expression a1*u1+a2*u2+a3*u3 to the vector form of dot product A.U, where ...
19
votes
4answers
2k views

Why does MatrixForm affect calculations?

This is a really newbie question, but it has me confused. Why does this code work without // MatrixForm and doesn't work with ...
9
votes
2answers
2k views

How to get Matlab data imported with the same dimensions?

I have some Matlab image data with the following dimensions (output is from Matlab): >> size(im) ans = 86 86 3 45 The data imports just fine ...