How to save each resultant matrix from a for loop

I want to pick each resultant value of K from the first loop and insert into the second loop one by one

clc
clear all

no_nodes = 5;

A = 8;
E = 1.9e6;
L = 36;
k = A*E/L;

th = [0,pi/4,pi/2,3/4*pi];

for i = 1:4 
    theta = th(i);
    s = sin(theta);
    c = cos(theta);
    angle_mat =[c.^2 s*c -c.^2 -s*c;
                s*c s.^2 -s*c -s.^2;
                -c.^2 -s*c c.^2 s*c ;
                -s*c s.^2 s*c s.^2 ];
    K = k*angle_mat;

end

zero_mat = zeros(no_nodes*2);

for i = [1 3 5 7]
    zero_mat(i:i+3,i:i+3)= K
    zero_mat = zeros(no_nodes*2);
end

zero_mat = 10×10

1.0e+05 * 2.1111 -2.1111 -2.1111 2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 2.1111 2.1111 -2.1111 2.1111 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

zero_mat = 10×10

1.0e+05 * 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2.1111 -2.1111 -2.1111 2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 2.1111 2.1111 -2.1111 2.1111 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

zero_mat = 10×10

1.0e+05 * 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2.1111 -2.1111 -2.1111 2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 2.1111 2.1111 -2.1111 2.1111 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

zero_mat = 10×10

1.0e+05 * 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2.1111 -2.1111 -2.1111 2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 -2.1111 2.1111 2.1111 -2.1111 0 0 0 0 0 0 2.1111 2.1111 -2.1111 2.1111

as it can be seen that at the moment it is only picking the last resultant matrix and putting it in the second loop

Answer 1

[Matt J]

One way

no_nodes = 5;

A = 8;
E = 1.9e6;
L = 36;
k = A*E/L;

th = [0,pi/4,pi/2,3/4*pi];

K=cell(1,4);
for i = 1:4 
    theta = th(i);
    s = sin(theta);
    c = cos(theta);
    angle_mat =[c.^2 s*c -c.^2 -s*c;
                s*c s.^2 -s*c -s.^2;
                -c.^2 -s*c c.^2 s*c ;
                -s*c s.^2 s*c s.^2 ];
    K{i} = k*angle_mat;
end


zero_mat = zeros(no_nodes*2);

for j = 1:4
    i=2*j-1;
    zero_mat(i:i+3,i:i+3)= K{j}
    zero_mat = zeros(no_nodes*2);
end

[Amir Khan]

Thank you very much for the response. I was stuck on this for last week.

I understand you must be busy but can you please briefly explain the changes that you made?

[Matt J]

We are now saving the matrices K to a cell array,

K{i} = k*angle_mat;

from which we can easily recover them in the second loop.

[Amir Khan]

Sorry, I forgot to mention that The resultant matrices from the second loop is required to be saved individually like the first one. I applied the same method for the second loop but it says that it doesnt support brace indices.

clc;
clear all;

no_nodes = 5;
A = 8;
E = 1.9e6;
L = 36;
k = A*E/L;
th = [0,pi/4,pi/2,3/4*pi];
K=cell(1,4);
for i = 1:4 
    theta = th(i);
    s = sin(theta);
    c = cos(theta);
    angle_mat =[c.^2 s*c -c.^2 -s*c;
                s*c s.^2 -s*c -s.^2;
                -c.^2 -s*c c.^2 s*c ;
                -s*c s.^2 s*c s.^2 ];
    K{i} = k*angle_mat;
end
zero_mat = cell(1,4)
for j = 1:4
    i=2*j-1;
    zero_mat = zeros(no_nodes*2);
    zero_mat(i:i+3,i:i+3)= K{j}
    zero_mat{j}=zero_mat
end

[Matt J]

You could do,

zero_mat = zeros(no_nodes*2, no_nodes*2,4);
for j = 1:4
    i=2*j-1;
    zero_mat(i:i+3,i:i+3,j)= K{j};
end

[Amir Khan]

Thank you very much good sir!