There is an error in drawing the graph!

n=41;     h=1/(n-1);    nt=360;       tau=0.001;
for i=1:n 
    x(i)=(i-1)*h;
    y(i)=(i-1)*h;  
end  

for j=1:n
    for i=1:n 
        p0(i,j)=1;    
    end   
end

for jt=1:nt 
    t(jt)=jt*tau; 
    for j=1:n   % Anlitik yechimni hisoblash
        for i=1:n 
            pt(i,j)=exp(-2*x(i)*y(j)*t(jt));
        end      
    end 
end
tic     
for jt=1:nt/2    % Vaqt bo`yicha tsikl}          
    
    [po,pp]=fxy(n,tau,h,p0,x,y,t,jt);
    [po,pp]=fyx(n,tau,h,p0,x,y,t,jt);
    
end % jt
toc 

for j=1:n
    px(j)=pp(21,j); 
    pxt(j)=pt(21,j);
end             

x=0:h:1;
y=0:h:1;
figure ('Position',[600 160 700 600]); %Natijalarni figuraga chiqarish oynasi: 750-eni, 650-boyi, 700-chapdan masofa, 75-yuqoridan masofa  

subplot(3,2,1);
meshc(x,y,pt) %Uch o'lchovli 3D grafika
title('АНИК ЕЧИМ 3D ГРАФИГИ')

subplot(3,2,2);
meshc(x,y,pp) %Uch o'lchovli 3D grafika
title('CОНЛИ ЕЧИМ 3D ГРАФИГИ')

subplot(3,2,3);
contour(x,y,pt,'ShowText','on','LineWidth',2); %kontur chizish 
title('АНИК ЕЧИМ КОНТУР ГРАФИГИ')

subplot(3,2,4);
contour(x,y,pp,'ShowText','on','LineWidth',2); %kontur chizish 
title('CОНЛИ ЕЧИМ КОНТУР ГРАФИГИ')

subplot(3,2,5);
plot(x,px,x,pxt); %Ikki o'lchovli grafika 
title('КЕСИМДА АНИК ВА CОНЛИ ЕЧИМ ЎЗГАРИШИ X БЎЙИЧА')


function [p0,p] = fxy(n,tau,h,p0,x,y,t,jt)

% k+0.5 vaqt qatlamida hisoblash
for j=2:n-1     % Tenglamalar koeffitsientini hisoblash 
    for i=2:n-1  
        %chekli ayirma tenglama koeffitsentlarini hisoblash  
        a(i)=1;
        c(i)=1;
        b(i)=2+2*h*h/tau;
        ff=h*h*(-2*(2*t(jt)*t(jt)*(x(i)*x(i)+y(j)*y(j))+x(i)*y(j))*exp(-2*x(i)*y(j)*t(jt)));   
        d(i)=2*h*h/tau*p0(i,j)+(p0(i,j-1)-2*p0(i,j)+p0(i,j+1))+ff;  
    end
    %Pragonka koeffitsentlarini hisoblash 
    aa1(1)=0; bb1(1)=1;    
    for i=2:n-1
        aa1(i)=c(i)/(b(i)-aa1(i-1)*a(i));
        bb1(i)=(d(i)+bb1(i-1)*a(i))/(b(i)-aa1(i-1)*a(i));
    end
    % bosim funktsiyasini hisoblash   
    p(n,j)=exp(-2*y(j)*t(jt));  
    for i=n-1:-1:1 
        p(i,j)=aa1(i)*p(i+1,j)+bb1(i);
    end                   
end %j    

for i=1:n % Chegaraviy qiymatlarni hisoblash 
    p(i,n)=(4.0*p(i,n-1)-p(i,n-2))/3;
    p(i,1)=(4.0*p(i,2)-p(i,3))/3;
end      

for j=1:n  % k+1 qatlam uchun boshlangich qiymatni hisoblash  
    for i=1:n      
        p0(i,j)=p(i,j);  
        
    end  
end         

% k+1 vaqt qatlamida hisoblash
for i=2:n-1    % Tenglamalar koeffitsientini hisoblash 
    for j=2:n-1  
        %chekli ayirma tenglama koeffitsentlarini hisoblash       
        a(j)=1;
        c(j)=1;
        b(j)=2+2*h*h/tau;
        ff=h*h*(-2*(2*t(jt)*t(jt)*(x(i)*x(i)+y(j)*y(j))+x(i)*y(j))*exp(-2*x(i)*y(j)*t(jt)));   
        d(j)=2*h*h/tau*p0(i,j)+(p0(i-1,j)-2*p0(i,j)+p0(i+1,j))+ff; 
    end
    %Pragonka koeffitsentlarini hisoblash 
    aa1(1)=0; bb1(1)=1;  
    for j=2:n-1 
        aa1(j)=c(j)/(b(j)-aa1(j-1)*a(j));
        bb1(j)=(d(j)+bb1(j-1)*a(j))/(b(j)-aa1(j-1)*a(j));
    end
    % bosim funktsiyasini hisoblash   
    p(i,n)=exp(-2*x(i)*t(jt));  
    for j=n-1:-1:1 
        p(i,j)=aa1(j)*p(i,j+1)+bb1(j);
    end    
end  %i             

for j=1:n  % Chegaraviy qiymatlarni hisoblash 
    p(n,j)=(4.0*p(n-1,j)-p(n-2,j))/3;  
    p(1,j)=(4.0*p(2,j)-p(3,j))/3;          
end        

for i=1:n   % keyingi qatlam uchun boshlangich qiymatni hisoblash 
    for j=1:n      
        p0(i,j)=p(i,j);  
    end  
end       
end

function [p0,p] = fyx(n,tau,h,p0,x,y,t,jt)
% k+1 vaqt qatlamida hisoblash
for i=2:n-1    % Tenglamalar koeffitsientini hisoblash 
    for j=2:n-1  
        %chekli ayirma tenglama koeffitsentlarini hisoblash       
        a(j)=1;
        c(j)=1;
        b(j)=2+2*h*h/tau;
        ff=h*h*(-2*(2*t(jt)*t(jt)*(x(i)*x(i)+y(j)*y(j))+x(i)*y(j))*exp(-2*x(i)*y(j)*t(jt)));   
        d(j)=2*h*h/tau*p0(i,j)+(p0(i-1,j)-2*p0(i,j)+p0(i+1,j))+ff; 
    end
    %Pragonka koeffitsentlarini hisoblash 
    aa1(1)=0; bb1(1)=1;  
    for j=2:n-1 
        aa1(j)=c(j)/(b(j)-aa1(j-1)*a(j));
        bb1(j)=(d(j)+bb1(j-1)*a(j))/(b(j)-aa1(j-1)*a(j));
    end
    % bosim funktsiyasini hisoblash   
    p(i,n)=exp(-2*x(i)*t(jt));  
    for j=n-1:-1:1 
        p(i,j)=aa1(j)*p(i,j+1)+bb1(j);
    end    
end  %i             

for j=1:n  % Chegaraviy qiymatlarni hisoblash 
    p(n,j)=(4.0*p(n-1,j)-p(n-2,j))/3;  
    p(1,j)=(4.0*p(2,j)-p(3,j))/3;          
end        

for i=1:n   % keyingi qatlam uchun boshlangich qiymatni hisoblash 
    for j=1:n      
        p0(i,j)=p(i,j);  
    end  
end       

% k+0.5 vaqt qatlamida hisoblash
for j=2:n-1     % Tenglamalar koeffitsientini hisoblash 
    for i=2:n-1  
        %chekli ayirma tenglama koeffitsentlarini hisoblash  
        a(i)=1;
        c(i)=1;
        b(i)=2+2*h*h/tau;
        ff=h*h*(-2*(2*t(jt)*t(jt)*(x(i)*x(i)+y(j)*y(j))+x(i)*y(j))*exp(-2*x(i)*y(j)*t(jt)));   
        d(i)=2*h*h/tau*p0(i,j)+(p0(i,j-1)-2*p0(i,j)+p0(i,j+1))+ff;  
    end
    %Pragonka koeffitsentlarini hisoblash 
    aa1(1)=0; bb1(1)=1;    
    for i=2:n-1
        aa1(i)=c(i)/(b(i)-aa1(i-1)*a(i));
        bb1(i)=(d(i)+bb1(i-1)*a(i))/(b(i)-aa1(i-1)*a(i));
    end
    % bosim funktsiyasini hisoblash   
    p(n,j)=exp(-2*y(j)*t(jt));  
    for i=n-1:-1:1 
        p(i,j)=aa1(i)*p(i+1,j)+bb1(i);
    end                   
end %j    

for i=1:n % Chegaraviy qiymatlarni hisoblash 
    p(i,n)=(4.0*p(i,n-1)-p(i,n-2))/3;
    p(i,1)=(4.0*p(i,2)-p(i,3))/3;
end      

for j=1:n  % k+1 qatlam uchun boshlangich qiymatni hisoblash  
    for i=1:n      
        p0(i,j)=p(i,j);  
    end  
end         

end

The graph looks like this.

The graphic should actually be like that!

Answer 1

[Benjamin Thompson]

Here you are drawing two lines:

subplot(3,2,5);

plot(x,px,x,pxt); %Ikki o'lchovli grafika

title('КЕСИМДА АНИК ВА CОНЛИ ЕЧИМ ЎЗГАРИШИ X БЎЙИЧА')

If you only intend to draw one line, remove the second dataset:

plot(x, px);

[Shikhnazar Ismailov]

Both graphics need to be released!

[Shikhnazar Ismailov]

The second function takes the values of p and p0 derived from the first function. The first function takes the values of p and p0 derived from the second function. Only in the beginning does the first function work with the above values of p and p0, otherwise it must calculate the mutual exchange. How can I do this?