My plot won't show any graph

I try to plot the data i get from step below. But My plot doesn't have any data. Just a clean sheet. Can anyone tell which part I'm wrong

clear
%%Given :
T= 5;
del_t=0.5;
t=0:del_t:T;

E=5;
v=0.3;
Sya=25;
Sy=15;
d=0.4;
vis=0;
gamma=0;

%Assume :
epn=0;
alfa=0;
DevS=0;

M= E/(2*(1+v));
L= (E*v)/[(1+v)*(1-2*v)];
G = norm(DevS)-sqrt(2/3)*Sy+(Sya-Sy)*(1-exp(-d*alfa))-[M*gamma*2];
Gd=-2*M*(1+(Sya-Sy)*d*exp(-d*gamma));

for n = 1:length(t);
  
    strain=6*n*[1 0 0; 0 1 0; 0 0 1]+6*sin(n)*[0 2 0; 2 1 0; 0 0 3/2];
    el=strain-(1/3)*trace(strain)*eye(3,3);%
    DevStrial=DevS+2*M*(el-epn); %Devatoric Stress Trial
    etrial=DevStrial; 
    
  y=Sy+(Sya-Sy)*(1-exp(-d*alfa));
    ftrial=norm(DevS)-sqrt(2/3)*y;
if ftrial<=0;
    DevS=DevStrial;
else
    
     while and((abs((G/Gd)/gamma)) >= 0.001, gamma==0);
%g[dγ(k)]
G = ftrial-[M*gamma*2];
%Dg[dγ(k)]
Gd=-2*M*(1+(Sya-Sy)*d*exp(-d*gamma));
 gamma= gamma - G/Gd;
% Derivative of yield limit function: K'(α)

end
    del_g= gamma;
    normal=etrial/norm(etrial);
    alfa=alfa+sqrt(2/3)*del_g;
    
%Update back stress, plastic strain, and stress
epn=epn+del_g*normal;
k = L+(2/3)*M;
S=k*trace(strain)*eye(3,3)+DevStrial-2*M*del_g;

% Compute consistent elastoplastic tangent moduli
A=eye(3,3);
B=eye(6,6);
Cp=1/3*kron(A,A)-kron(normal,normal);

end
end

figure
hold on
plot(t,S(1:1,1:1),'linewidth',5,'color','r')
plot(t,S(2:2,2:2),'linewidth',5,'color','r')
plot(t,S(3:3,3:3),'linewidth',5,'color','r')
legend('s11','s22','s33')

plot(t, alfa ,'linewidth',5,'color','r')
xlabel( 'Time', 'FontSize', 16)
ylabel( 'alfa', 'FontSize', 18)
grid on

figure
hold on
plot(t,Cp(1:1,1:1),'linewidth',5,'color','r')
plot(t,Cp(4:4,4:4),'linewidth',5,'color','r')
plot(t,Cp(5:5,5:5),'linewidth',5,'color','r')
legend('s1','s2','s3')

Answer 1

[VBBV]

clear
%%Given :
T= 5;
del_t=3;
t=linspace(0,T,del_T); 

E=5;
v=0.3;
Sya=25;
Sy=15;
d=0.4;
vis=0;
gamma=0;

%Assume :
epn=0;
alfa=zeros(size(t));
DevS=0;

M= E/(2*(1+v));
L= (E*v)/[(1+v)*(1-2*v)];
G = norm(DevS)-sqrt(2/3)*Sy+(Sya-Sy)*(1-exp(-d*alfa))-[M*gamma*2];
Gd=-2*M*(1+(Sya-Sy)*d*exp(-d*gamma));

for n = 1:length(t);
  
    strain=6*n*[1 0 0; 0 1 0; 0 0 1]+6*sin(n)*[0 2 0; 2 1 0; 0 0 3/2];
    el=strain-(1/3)*trace(strain)*eye(3,3);%
    DevStrial=DevS+2*M*(el-epn); %Devatoric Stress Trial
    etrial=DevStrial; 
    
  y=Sy+(Sya-Sy)*(1-exp(-d*alfa));
    ftrial=norm(DevS)-sqrt(2/3)*y;
if ftrial<=0;
    DevS=DevStrial;
else
    
     while and((abs((G/Gd)/gamma)) >= 0.001, gamma==0);
%g[dγ(k)]
G = ftrial-[M*gamma*2];
%Dg[dγ(k)]
Gd=-2*M*(1+(Sya-Sy)*d*exp(-d*gamma));
 gamma= gamma - G/Gd;
% Derivative of yield limit function: K'(α)

end
    del_g= gamma;
    normal=etrial/norm(etrial);
    alfa(n)=alfa(n)+sqrt(2/3)*del_g;
    
%Update back stress, plastic strain, and stress
epn=epn+del_g*normal;
k = L+(2/3)*M;
S=k*trace(strain)*eye(3,3)+DevStrial-2*M*del_g;

% Compute consistent elastoplastic tangent moduli
A=eye(3,3);
B=eye(6,6);
Cp=1/3*kron(A,A)-kron(normal,normal);
end
end

% figure plots
figure(1)
plot(t,S(1:3,1:3),'linewidth',5,'color','r')
legend('s11','s22','s33')
hold on
plot(t, alfa ,'linewidth',5,'color','r')
xlabel( 'Time', 'FontSize', 16)
ylabel( 'alfa', 'FontSize', 18)
grid on

figure(2)
plot(t,Cp(1:3,1:3),'linewidth',5,'color','r')
legend('s1','s2','s3')

Answer 2

[Jan]

I assume, this is an effect or drawing a line with just 1 point, which produces no line.

Try

plot(t, S(1,1), 'linewidth', 5, 'color', 'r', 'Marker', 'o')

[Steve]

It still doesn't work, the S function is a matrix 3x3, and I want to plot the value of the first row and first column when t=0 till t=5

[Jan]

The first row is S(1, :), not S(1:1, 1:1).

What about:

plot(t,S,'linewidth',5,'color','r')