Make Matrix which Containing Matrix in MATLAB

Question

I want to create matrix in MATLAB like this which Identitas is identity matrix, Nol is zero matrix, min1 and mina is defined in the this code MATLAB below.

clear all;
clc;
h=0.2;
x=0:h:2;
k=0.2;
t=0:k:2;
N=length(x);
J=length(t);
a=4*h^2/k;
Identitas=eye(N,N);
Nol=zeros(N,N);
min1=zeros(N,N);
for i=2:N
    for j=2:N
        if i==j
            min1(i,j)=-1;
        end
    end
end
mina=zeros(N,N);
mina(1,1)=1;
for i=2:N
    mina(i,i-1)=-a;
    mina(i,i)=a+2;
end
MK(1,1)=Identitas;
for j=2:J-1
    MK(j,j-1)=min1;
    MK(j,j)=mina;
    MK(j,j+1)=min1;
end
MK(J,J)=Identitas;

That code give me error, because MATLAB cannot store a matrix in the array. So how to make that matrix in MATLAB?

rinkert rinkert · Accepted Answer · 2019-08-24T14:54:35

An easy fix would be to initialize MK as a cell array containing zero N-by-N matrices, fill in the right cells, and then convert it to a matrix using cell2mat:

MK = repmat({zeros(N,N)}, [J J]);   % initialize a J-by-J cell containing N-by-N zero matrix
MK{1,1}=Identitas;
for k=2:J-1
    MK{k,k-1}=min1;
    MK{k,k}=mina;
    MK{k,k+1}=min1;
end
MK{J,J}=Identitas;

MK = cell2mat(MK);                  % convert cell to matrix

Right now you are constructing min1 and mina using for-loops, but consider using the functions diag and blkdiag.

Make Matrix which Containing Matrix in MATLAB

1 Answers