Questions on the manipulation of matrices in Mathematica.

learn more… | top users | synonyms (1)

1
vote
1answer
59 views

Computation time depends on the matrix elements!

Consider these two lists of matrices, matrix and matrix2: ...
15
votes
2answers
399 views

Why is my data 10 times slower than random data when doing matrix multiplication

I have some data generated from some program, and it appears that matrix multiplication on these data are about 10 times slower than on some random data: ...
1
vote
1answer
88 views

Efficient method of raising matrix to a variable power?

I have a $2 \times 2$ matrix $A$, where each element is a 12th order polynomial in a parameter $a$. I need to raise this matrix $A$ to the $-t/T$ power, where $T$ is a known scalar (for this ...
2
votes
2answers
102 views

specified matrix query

can you tell me a way (best?) to get a matrix with i=N,j=N dimensions (quadratic) according to the following rules: variables: N , M, n the diagonal must contain zeros it must contain exactly M ...
4
votes
1answer
193 views

Table and memory efficiency

Consider these two types of creating matrices: Table[Table[i*j,{i,1,10}],{j,1,10}] Table[i*j,{i,1,10},{j,1,10}] I want to know if there is any difference ...
4
votes
1answer
182 views

Fast matrix multiplication in MMA and GPU

Matlab multiplies two 3000by3000 matrix around 0.18s faster than MMA. While for just a few matrix multiplications the speed difference is not important, it becomes crucial when I want to do those ...
0
votes
1answer
335 views

How to take transpose of a one dimensional vector? [closed]

Why the two followings giving me same output? At least one should give me a row vector and another should give me a column vector. MatrixForm[u = {1 , 1, -1, 1}] MatrixForm[v = {{1}, {1}, {-1}, ...
5
votes
3answers
269 views

Multiplying block matrices

I have a 2*8 matrix A, and a 2*8*2 matrix B. So B[[1]] and B[[2]] are both 8*2 matrices. I need a neat way to multiply A by B so that the first list in the result is A.B[[1]] and the second list ...
2
votes
1answer
109 views

Rescaling and reorienting Matrix Plot axes

I have implemented a numeric Laplace Solver in C++ and am trying to graphically represent the validity of my method. I have outputted the grid from C++ and imported it into Mathematica to get the ...
0
votes
2answers
93 views

Obtaining the relations of variables using diagonal matrices

I know this is too an elementary question, but I am a pathetic newbie in mathematica and I cannot find any answer by googling. What I want is obtaining some relations of unknown variables using their ...
3
votes
1answer
97 views

Print array with indices

Is there a single function that prints an array together with the indices? I know how to achieve this with Grid[{Range[n],array},Frame->All], but I vaguely ...
0
votes
0answers
77 views

solving singular matrix [duplicate]

Hello I have a matrix that is singular, and i wanted to use linear solve to solve it but that doesn't work with mathematica. The matrix given as a list looks like this: ...
0
votes
0answers
38 views

parsed matrix not deleting elements in adjusted matrix

I have a matrix that has been parsed to delete certain rows and columns, as well as delete certain elements on the diagonal on the matrix. The problem is that it does this in theory when i take the ...
0
votes
1answer
91 views

Matrix form of complex numbers [closed]

Complex numbers have matrix form. But some 2x2 matrices while differ, represent the same complex number. To compare complex numbers one has to transform the matrices to the form \begin{pmatrix} a ...
2
votes
1answer
99 views

Design matrix rank does not match

I'm attempting to fit a linear model and Mathematica returns the error message: "The rank of the design matrix 9 is less than the number of terms 10 in the model. The model and results based upon it ...
3
votes
2answers
103 views

How to reflect the entries of a square matrix about its anti-diagonal?

I need help with writing the mathematica code to reflect the entries of a square matrix about its anti-diagonal. I know to do it about the main diagonal using ...
0
votes
1answer
58 views

Why is there a seeming discrepancy with the expression Cofactor?

I was trying to find out the cofactors of a square matrix. Then I came across the command Cofactor in Combinatorica package. ...
2
votes
1answer
142 views

Computing with matrix differential operators

I am looking the achieve a working set of Mathematica functions that would allow me to take products, commutators, etc. of (2x2) matrix differential operators and apply them to vector-valued functions ...
0
votes
0answers
75 views

How to assign equation solutions to variables [duplicate]

I have 12x12 Matrix with which I have to solve the equation below: ...
3
votes
2answers
107 views

Help with building matrices

I am a complete beginner in Mathematica and I have a small problem. I have this three matrices (A,B and C) and with them I have to build larger matrix M which looks like this. What would be the ...
1
vote
0answers
103 views

Fast export of large numerical data

Edit It seems that the bottelneck is not due to eigen value problem. I will esit the question soon. I have a 6000by6000 matrix which I got after some calculations. I want to get the eigenvalues and ...
1
vote
2answers
72 views

how to get continuation of square matrices with periodic diagonal band automatically?

I want write a function that can automatically analyze any square matrices with periodic band diagonals and give continuations of them. But I can't figure out an elegant way to do this. Suppose we ...
2
votes
1answer
67 views

Anyone knows the algorithm used by NullSpace function?

NullSpace function gives a list of vectors that forms a basis for the null space of the input matrix. When the rank of the input argument matrix $M_{m\times n}$ is ...
2
votes
3answers
203 views

How to find the kth largest eigenvalue of a matrix, taking into account the sign? [duplicate]

I have a real symmetric matrix m (i.e. its eigenvalues are all real). Eigenvalues[m, {k}] will find the ...
1
vote
2answers
193 views

Get inverse of a matrix step-by-step [duplicate]

How can I get the inverse of a matrix step by step? An example: Given the matrix `{{8, 2}, {3, 2}}´, the result is {{$\frac{1}{5}$, -$\frac{1}{5}$}, {-$\frac{3}{10}$, $\frac{4}{5}$}}. But how can I ...
1
vote
1answer
95 views

How to add an extra column to a current matrix (list)? [duplicate]

a = {{-800, 1712}, {-801, 1713}, {-806, 1832}} TableForm[a] b = a[[All, 2]] - Min[a[[All, 2]]] How do I make a new matrix (list) whic looks like this ...
1
vote
1answer
123 views

Correlation to Covariance Matrix

I am looking to use the CopulaDistribution fucntion, with a "MultiNormal" kernal. However, for the input, O require a covariance matrix. However, I only have a correlation matrix. Is there a way to ...
1
vote
2answers
62 views

Table operation after export and import of data does not give me the same result

If I create a table of this kind: (m1 = Table[{RandomInteger[], RandomInteger[{1, 5}, {3}]}, {i, 1, 5}]) // MatrixForm which looks like I know how to pick ...
3
votes
2answers
108 views

Eigenvectors of large symbolic matrix

I have large symbolic matrix of order 32 x 32 given as ...
1
vote
0answers
130 views

Best way to create symmetric matrices with block structure and additional symmetries of the submatrices

Update: you can now skip the "My attempted solution" part and jump to "My first attempt for improvement" in the end of the question. My question is related to Best way to create symmetric matrices . ...
0
votes
1answer
63 views

How to use Hold on a variable defined as a graph

I'm working on doing operations on different graphs and getting their probability node degree distributions using a simple algorithm. If I have many defined graphs, for example: ...
2
votes
2answers
62 views

Findings rows in RREF matrix which contain nothing but a pivot

I am asked to find all rows in a matrix in reduced row echelon form which contain nothing but pivots (pivot is $1$, all other entries are $0$). For example, in this matrix: $$ \begin{bmatrix} 1 ...
1
vote
0answers
46 views

Dealing with answers that have Root[ …] when finding an Eigensystem [duplicate]

This is a 3x3 matrix and I think it should solve for the expressions in terms of radicals. I am not sure what to do with this.
-2
votes
1answer
57 views

Create a matrix by crossing a list

I've a list L of elements. I want to create a matrix by laying each elements of L in both rows and columns where each ...
0
votes
1answer
58 views

Problem in LinearProgramming [closed]

I wrote a integer Linear programming where matrix c, m and b are: ...
1
vote
3answers
130 views

Matrices and Combination

When the positive integers 1 to 9, inclusive, are used exactly once as elements of a 3 x 3 matrix, what is the largest possible value of the determinant of the matrix?
1
vote
0answers
72 views

Lens profile in a grid

So I have a FDTD code which works and its all good the propagator of the code it self is: ...
0
votes
1answer
33 views

dropOperator done on Matrix of a Matrix - How is this done?

I have implemented this dropOperator from dropOperator from stackexchange and works fine on a single Matrix. But now I have a Matrix of a Matrix and want to drop some rows or columns (in the pic below ...
0
votes
1answer
111 views

Block matrix and calculate it's inverse

How to define the following block matrix $$ A=\begin{bmatrix} H-G_1 & -G_1 & \ldots & -G_1 \\ -G_2 & H-G_2 & \ldots & -G_2 \\ \vdots & \ldots & \vdots & \vdots ...
0
votes
0answers
121 views

Solving for a Transfer Matrix

I am currently working on a program that will solve a transfer matrix and extract several elements. Particularly, the transfer matrix is characterized by four elements in a ...
1
vote
1answer
102 views

How to print non zero elements of the matrix containing zero elements and non-zero elements both?

A matrix with both non-zero and zero elements is given. I want to print only the non-zero elements of the matrix. What is syntax that have to be used for this? matr2 = Table[FortranForm[matrixx[[i, ...
2
votes
2answers
92 views

Find the indexes of dependent columns

I have a fairly large singular square matrix, of size 37 and rank 35. Is there a way to get a vector with the (groups of) indexes of the columns in the original matrix that are linearly dependent? ...
1
vote
2answers
91 views

How to extract matrix which produces given symbolic linear combinations?

Suppose I have a column matrix $\alpha$, consisting of some symbols ...
1
vote
1answer
69 views

Entering block matrices, general case doesn't work

I want to enter several matrices at different positions in blocks. There is already a very similar answer here: http://mathematica.stackexchange.com/a/3562/6138 I thought that simply generalizing ...
1
vote
1answer
80 views

What does it mean: “Assuming a matrix | Use a list of lists instead”?

I have entered a matrix by Insert->Table/Matrix->New. After adding it to code, Mathematica wrote a remark: "Assuming a matrix | Use a list of lists instead". ...
1
vote
2answers
47 views

How to add a part of a list to a function?

I want to be able to add a specific portion of a list to a part of a function but this fucntion intakes 6 variables where as the list is of example: ...
3
votes
0answers
91 views

Understanding polyharmonic splines

Raul Narain and J.M. gives implementation of the thin plate polyharmonic splines in this post. Raul Narian's method is clear. J.M.'s is convenient to reuse. But J.M. used too many ...
0
votes
1answer
63 views

LinearSolve in Mathematica, used to find square matrix

Another issue I have with Mathematica today is that I want to solve the following matrix equation: X.b=c where b and c are two vectors, and X is a square ...
1
vote
1answer
55 views

How to indroduce a value for the functions inside a matrix? [closed]

I would like to assign certain values to the X and Y variables which are inside the functions in the matrix. Thus, I would like to get a matrix with values based on the transformation in Psi matrix. ...
2
votes
1answer
206 views

Log of a Matrix

I have used the command MatrixLog[m] But it gives natural log of the matrix. How can I find the Log (to the base 2) of a matrix?