MATLAB: “Kronecker” of varying dimensions

kronkroneckermatricesmatrixmatrix manipulation

Hi, I have a matrix A of dimension m x n and a vector b of natural numbers with dimension m x 1. I want to obtain a matrix C of dimension (b(1)+…+b(m)) x n by vertically stacking each A(i,:) b(i) times. For example:

A=[1 2 3; 4 5 6; 7 8 9];
b=[2; 1; 4];

I want to obtain

C=[1 2 3; 1 2 3; 4 5 6; 7 8 9; 7 8 9; 7 8 9; 7 8 9];

I cannot use loops.

Best Answer

A=[1 2 3; 4 5 6; 7 8 9] 
b=[2; 1; 4] 
out=cell2mat(arrayfun(@(x) repmat(A(x,:),b(x),1),(1:size(A,1))','un',0))

Related Solutions

MATLAB: Symmetric Kronecker product in Matlab

Hi Marcelo,

Here is an attempt at symmetric kron of square matrices A and B of the same size. The whole task is to make the matrices U. I have not verified this but it gives the correct result for U when A and B are 2x2 and 3x3. Also for 10x10, symmetric kron of A,B and of B,A give the same answer.

n = 10;
A = rand(n,n);
B = rand(n,n);
M1 = sk(A,B);
M2 = sk(B,A);
siz = size(M1)
max(max(abs(M1-M2)))
function M = sk(A,B)
% symmetric kronecker product for two square matrices, each of size nxn
n = size(A,1)
U = eye(n^2);
a = reshape(1:n^2,n,n);
b = a';
U = U + U(b(:),:);
c = tril(a);
c = c(:);
c(c==0) = [];
U = U(c,:);
U(U==1) = sqrt(2);
U(U==2) = 1;
M = (1/2)*U*kron(A,B)*U';
end

MATLAB: Kronecker product by number of iteration

Unless you are looking for a way to do this in one line of code, a simple for loop would do the trick

A = [1 2;3 4];
B = A;
for k=1:5
    B = kron(B,A);
end

Best Answer

Related Solutions

MATLAB: Symmetric Kronecker product in Matlab

MATLAB: Kronecker product by number of iteration

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