Expanding a complex element to a matrix
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Hi,
I have a complex matrix and I would like to convert the matrix to the real and imaginary components without changing the location. Say the complex matrix is
[A11 A12;
A21 A22]
each Aij = Gij + 1j* Bij. After expanding the matrix, I would get my desire matrix as
[[G11 -B11;B11 G11] [G12 -B12;B12 G12] ;
[G21 -B21;B21 G21] [G22 -B22;B22 G22]]
In the code below, the variable B indicates what I want to achieve, but I want to do it more efficiently than via a for loop and the i*2 indicator.
clear
clc
nb=2;
A=complex(magic(nb),1./magic(nb));
% tic
Ar=real(A);
Ai=imag(A);
B=zeros(2*nb,2*nb);
for i=1:nb
for j=1:nb
B(2*i-1,2*j-1)= Ar(i,j);
B(2*i-1,2*j) =-Ai(i,j);
B(2*i,2*j-1) = Ai(i,j);
B(2*i,2*j) = Ar(i,j);
end
end
% toc
Any advice would be much appreciated. Thanks for reading.
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Accepted Answer
Matt J
on 17 Jan 2017
Ar=real(A);
Ai=imag(A);
B=zeros(2*nb,2*nb);
B(1:2:end,1:2:end)=Ar;
B(1:2:end,1:2:end)=Ar;
B(1:2:end,2:2:end)=-Ai;
B(2:2:end,1:2:end)=Ai;
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