Questions on the manipulation of matrices in Mathematica.

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4
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1answer
412 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 ...
1
vote
1answer
2k 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. ...
2
votes
1answer
240 views

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) ...
5
votes
3answers
351 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 ...
3
votes
1answer
230 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
96 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
157 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
92 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
43 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
139 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
177 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 ...
5
votes
2answers
201 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
101 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
272 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
140 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
110 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 ...
2
votes
0answers
206 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
95 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
132 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
515 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
440 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
305 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 ...
3
votes
0answers
156 views

The CorrelationMatrix is equal to corrcoef of Matlab?

How can I generate a matrix which is equivalent to the results of the "correlation coefficients" command (corrcoef) in Matlab? When I make a LinearModelFit, I can get a CorrelationMatrix, but is this ...
1
vote
1answer
238 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
119 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
138 views

Eigenvectors of large symbolic matrix

I have large symbolic matrix of order 32 x 32 given as ...
2
votes
0answers
198 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
81 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
101 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
47 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
62 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 ...
1
vote
3answers
156 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?
0
votes
1answer
37 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
2answers
176 views

Block matrix definition and inversion

I would like 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 & ...
1
vote
1answer
139 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
144 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
109 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
83 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
103 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
53 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
2answers
263 views

Understanding polyharmonic splines

Rahul Narain and J.M. gives implementation of the thin plate polyharmonic splines in this post. Rahul Narain's method is clear. J.M.'s is convenient to reuse. But J.M. used too many ...
0
votes
1answer
117 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 ...
2
votes
2answers
332 views

Logarithm of a matrix in base 2?

Mathematica provides the built-in command MatrixLog, which operates on a square nonsingular matrix, but it returns the natural logarithm. How can I find the base 2 ...
2
votes
1answer
86 views

Sort a vector of vectors of vectors

Let's hope I'm calling it well, I have this vector, or matrix, now I really don't know what it is ...
1
vote
0answers
49 views

Displaying a matrix as an array of solid rectangular blocks [duplicate]

I would like to plot an array of numbers as a surface, with each number the height of a square, and with the squares connected to adjacent squares with vertical rectangles, up or down as appropriate. ...
2
votes
1answer
135 views

Easy way to perform multiplication of two 2x2 matrices, that contain list elements?

I have two 2x2 matrices, which elements are lists (so overall structure can be complicated). I need to perform matrix multiplication of these 2x2 matrices as if the elements didn't have its inner ...
2
votes
1answer
200 views

matrix multiplication speed

Consider the codes below: ...
0
votes
2answers
47 views

Suggest how to do this matrix multiplication [duplicate]

Have a look at the Mathematica calculation ...
1
vote
1answer
130 views

Insert a linebreak and character repeatedly into a matrix output which is in fortranForm

Suppose I have a very long string which is a11 element of matrix a11=2*gopsv-2*Bgopsvw+2*acgmops*v+2*cgmopsv*B-2*acgmopsvB+3*gmopsvB-3*BgmopsvwB+m*w2*B +5*acgm2 +opsvB -ac*m2*w2*B +cgm2*opsvB* - ...
1
vote
0answers
44 views

How to show Output of matrix in FortranForm with “&” character?

I have a matrix. and i have shown the output of matrix one by one element in FortranForm. the problem is i want to put "&" continuation charater in output because when i am copying the data into ...