# Tagged Questions

Questions on the manipulation of matrices in Mathematica.

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### Symbolic matrix inversion

If I try to get an inverse of a matrix: a | b | c b | d | 0 c | 0 | 0 Inverse[{{a, b, c}, {b, d, 0}, {c, 0, 0}}] I get the answer: ...
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### Simplifying Terms in a Matrix

Given the following 3 matrices: M1=1/3*{{1,1,1},{1,α,α^2},{1,α^2,α]}} Z1={{Z+Zg,Zg,Zg},{Zg,Z+Zg,Zg},{Zg,Zg,Z+Zg}} M2={{1,1,1},{1,α^2,α},{1,α,α^2}} where alpha ...
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### Beginner Question: Assigning an indexed Variable to a given list

I am pretty new to the game and have a problem, which i am sitting on for hours. 1) I created a random Matrix 5x5 Q=Table[Q[i,j]=RandomReal[{0.6,1}],{i,5},{j, 5}] ...
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### Does Mathematica store hidden information for matrix objects?

Bug introduced in 10.0 and fixed in 10.2.0 I found a case where calling one built-in function (HermitianMatrixQ) for a given matrix changes the behavior of ...
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### Divide each element of a list of 500 matrices by another matrix

Lets say that I have a Table of dimension (3,3,500) and I'd like to perform element-wise division by a 3x3 matrix along the third dimension (of length 500 in this case). What is the most elegant way ...
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### Speed up the auxiliary function magicSquare when $n$ is doubly-even

Today, I saw a question about magic square (please see here). When $n$ is doubly-even, namely for Mod[n,4]==0 ...
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### Parametrizing a matrix given its trace and norm

I have a problem where I have to generate random matrices with the following properties: ($a$ is a given fixed number) $\mathrm{Tr}\, A=0$ $\mathrm{Tr}(A^\dagger A)=\|A\|_F^2=a$ I was wondering ...
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### Are variables always assumed to be real in Jordan Decomposition?

If you give the following input in Mathematica 9.0 (Student Edition): JordanDecomposition /@ ({{1, #}, {#, -1}} & /@ {i, I}) Mathematica gives you two ...
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### Counting variable from a list of matrices

I have a list of matrices ...
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### Gridding in a Nested Matrix

We have a nested matrix as: nested={{he, {{e, f, g, h}, {s, 0, q, i}, {s, 0, q, j}}}, {ho, {{e, f, g, h}, {0, u, t, i}, {u, t, 0, j}}}} and with the line <...
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### Usage of Piecewise/RSolve to solve an equation based on condition

I am trying to compute price of call option on a stock using the finite difference method. I have a VBA code for it, and I am trying to find out how I can use Mathematica memoization functions and ...
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### Recursive computation using Piecewise

I am trying to create an array using a series of equations using Piecewise. I am stuck in one of them. I am just putting a simplified version of code as below. I ...
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### Laplace equation

I tried to run this code, but it doesn't work for NDSolve ...
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### Deciphering output messages using Solve

I'm trying to solve the following system. The error messages I'm getting suggest that there may not be a solution [my desired result], but I'm not sure if there could be something else going on. The ...
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### Absolute VectorPlot scaling

I'm trying to visualize the vector components of a rotation matrix with absolute vector lengths. VectorScale help states that When using an explicit sfun, ...
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### Matrix iteration failing after second step

I am calculating 11x6 matrix using different logics as in below code. Problem is in Do loop in below code where I have two different criteria to update matrix "fd". I am expecting logic in IF which ...
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### Replace element of matrix based on rule which invloves other element of same matrix

I am trying to replace 1s row of matrix d iteratively from right by multiplying last element in 1st row with (1-int*dt) to generate 2nd last element. The replacement continues till I reach the 1st ...
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### Express block matrix in terms of matrix basis

I'm trying to construct a function that returns the multiplication table of a matrix Lie algebra. Assuming a basis of matrices, my definitions: ...
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### How can I get symbolic orthonormal eigenvectors for 3 by 3 hermitian matrix?

Using the following syntax, I can obtain the symbolic eigenvalues and eigenvectors of the following Hermitian matrix (a,b,c,d are all real parameters): ...
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### Recreating in Mathematica a matrix created in Python [closed]

I need to recreate in Mathematica this matrix that I created in Python: ...
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### Plotting six chosen rows of a matrix

I have a matrix,W, whose dimension is n x n, each entry is a number. I need to plot only the values of six rows, namely those ...
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### Calculating a function repetitively without using a For loop

In my programme I have defined all these functions: ...
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### Filing matrix by bands [closed]

I need to fill a matrix, CSI, by taking elements from an array, inverse, which is the Inverse Fast Fourier Transform of an array ...
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### sparse array with list [closed]

i'm trying to populate a sparse array with lists in certain positions, i tried the following code, ...
789 views

### Writing a circular matrix

I have two square matrices, $A$ and $B$, of the same size, say, of $m \times m$. What I want is to write a programme/function of three variables, $A$, $B$ and $n$, that outputs the $mn \times mn$ ...
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### How can I manipulate this list?

I performed a loop with Table where I solve a system of 4 equations that depends on two parameters: eta and p. I create two lists for each parameter as follows: <...
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### Defining a function of matrices [closed]

I am translating my code from Python to Mathematica. How can I define a function similar to the following: ...
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### Define a matrix depending on variable in Mathematica [closed]

I am translating my code from Python to Mathematica. I am trying to define a matrix, whose values depend on a variable chosen by the user, called kappa. In Python the code looked like that: ...
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### calculating subsets of a matrix (L=40X40)

I need to calculate all $k$-possible subsets$(k:1,L)$ of matrix with size $L$. I am using subset function as following, ...
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### How do I generate all $n\times m$ matrices s.t. $a_{i,j} \in {a … b}$?

Is there a fast and clean way of generating all possible $n\times m$ matrices s.t. $a_{i,j} \in \{a ... b\}$ - much like Range does in $N$? Consider for example that for $n,m = 2$, $a=0$, $b=2$ I ...
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### What is the “proper” way of multiplying a list of vectors by a matrix? Why Map does not work? [closed]

I am an absolute newbie with Mathematica, so please forgive me if this is stupid, but for the life of me I can't solve this. Suppose I have a list of vectors $b_{1...n}$ and a square matrix $A$ and I ...
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### Verify Cayley-Hamilton Theorem

Consider the matrix: A = {{-1, -4, -2}, {0, 1, 1}, {-6, -12, 2}} Now, the characteristic polynomial is found: ...
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### Unragging a matrix

Today I ran into matrices like this one: ...
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### Maximum element and its position (row,column) of matrix

Can someone help me to get the maximum element of $m\times n$ matrix and corresponding row and column $(i,j)$?
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### How to insert a Matrix into a larger matrix

I have a 4x4 matrix v1 v2 v3 v4 myM={{a1,a2,c1,c2}, v1 {a2,a3,c2,c3}, v2 {c1,c2,d1,d2}, v3 {c2,c3,d2,d3}} v4 And I want to ...
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### Counting and updating a subset of matrix

I have an n by n matrix and would like to count the number of sub-matrices that is equal to a given matrix. Here is my code: DWBCL creates a matrix with elements a1, a2 and c2 in it and DWBCH with b1, ...
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### Filling a matrix with a list of lists

I have a list of lists with different lengthes: {{a1,a2},{b1,b2},{c1,c2,c3},...} Now I want to create a matrix the following way: ...