Questions on the manipulation of matrices in Mathematica.

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3
votes
3answers
299 views

Correct way to populate a DiagonalMatrix?

I would like to create a series of correlation matrices that starts with : sensMat[[1]] = DiagonalMatrix[ { 1,1,1,1,1 } ]) // MatrixForm and iterates in 0.1 ...
5
votes
1answer
1k views

Problem with plotting eigenvalues

I want to plot the eigenvalues of a matrix which is dependant on a parameter (well, actually I want to plot a tight-binding electronic band structure). The dimension of the hamitonian matrix is ...
1
vote
3answers
774 views

How do I combine the data from two tables according to a rule of my own devising?

I have two matrices a = m x 5 and b =m x 5 (m is large, say 1,000) which are already sorted as below: How to generate a new matrix c = m x 5 which consists: Column 1: exact replica of Column 1 ...
-1
votes
2answers
381 views

Correct way to compare arrays and do conditional evaluations

I would like to compare two arrays a=: and b= and get: using: (b/.(b_?Positive->a+b))//MatrixForm but this doesn't seem to work? Can ...
0
votes
3answers
879 views

Correct way to remove matrix columns?

I start off with m = 1000 x 5 matrix, and I would like to remove first column to get 1000 x 4 matrix and repeat again for ...
-2
votes
1answer
118 views

Can Depth be used as an equivalent for MatrixQ?

Given an expression x, are the following two statements interchangable with no exceptions? Depth[x] - 1 == 2 ...
-1
votes
1answer
435 views

How to efficiently fill in matrix values?

I would like to efficiently fill in or assign values to matrix m: m={ {a[1,1],a[1,2],a[1,3],a[1,4]}, {a[2,1],a[2,2],a[2,3],a[2,4]}, {a[3,1],a[3,2],a[3,3],a[3,4]}, ...
2
votes
3answers
202 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? ...
2
votes
1answer
404 views

RowReduce: Solving for the resource vector (a, b, c) in Augmented Matrix

Here are two examples: RowReduce[{{3, 1, a}, {2, 1, b}}] evaluates to {{1, 0, a - b}, {0, 1, -2 a + 3 b}} but ...
0
votes
2answers
369 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: ...
9
votes
2answers
809 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 ...
4
votes
2answers
316 views

Rearranging a matrix

I would like to convert a matrix which has a structure like this: {{"A", 10, "D", 1},{"B", 3, "A", 2},{"C", 7, "B", 3},{"D", 6, "C", 4}}//MatrixForm//Print; ...
9
votes
1answer
279 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 ...
3
votes
3answers
187 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 ...
4
votes
2answers
570 views

Exact cover solution

Is it possible to get a exact cover solution(s) and/or number of possible solutions in Mathematica?
1
vote
0answers
296 views

Matrix algebra vs. PrincipalComponents and Varimax/Oblimin

Using matrix algebra I can calculate loadings and scores from the covariance matrix (data matrix is column centered): ...
5
votes
1answer
188 views
5
votes
2answers
434 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
327 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 ...
4
votes
2answers
1k views

I need to multiply a series of matrices

I need to perform a dot product on a large number of 2 x 2 matrices that I have defined to differ by even/odd subscripts (Ex: D-odd=x but D-even=y). The $\Pi$ function will not work because it does ...
7
votes
3answers
748 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 ...
7
votes
4answers
193 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 ...
3
votes
3answers
230 views

Are table headings functional?

Are table headings for aesthetics only? If I have: ...
1
vote
1answer
153 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
499 views
2
votes
1answer
346 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
244 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
421 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. ...
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
225 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
1answer
291 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: ...
2
votes
1answer
585 views
1
vote
2answers
702 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 ...
0
votes
2answers
120 views

Matrix conditional operation

Say I have a matrix of: tmp1 = 5; tmp2 = 5; tmp3 = RandomChoice[{0, 1, 2, 3, 4, 5}, {tmp1, tmp2}]; MatrixForm[tmp3] How to do a conditional operation of elements ...
0
votes
2answers
218 views

How to get a sub range of a larger matrix?

This should be an easy question but I only found a partial solution using All. Say I have a matrix A = 1000 x 5, how to get only a part of that matrix, say B = n x ...
2
votes
3answers
343 views

Is there a way to do conditional matrix loop using 'continue'

I have the following: ...
1
vote
1answer
518 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
240 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 ...
0
votes
1answer
550 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 ...
3
votes
0answers
203 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
169 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
496 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 ...
7
votes
3answers
404 views

How do we solve N-Rooks variation using primes?

Using a $p_n $x $p_n$ matrix, how can we solve the N-Rooks problem to find a prime in every row and column? ...
1
vote
0answers
239 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 (...
2
votes
1answer
286 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
2answers
732 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
585 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 ...
2
votes
2answers
291 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
267 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
2k 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 ...