How to change diagonal, subdiagonal and superdiagonal values with respect time while using loop and conditional statement?

Question

Yanni 2023-3-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1928275-how-to-change-diagonal-subdiagonal-and-superdiagonal-values-with-respect-time-while-using-loop-and

编辑： Yanni 2023-4-29

xmax=1; ymax=7; m=20; n=29; 
dx=xmax/m; dy=ymax/n; dt=0.2; 
UOLD=zeros(m,n);VOLD=zeros(m,n);
A=zeros([1,m]);
B=A;
C=A;
while dt<tmax
    for j=1:n
        for i=1:m
            if j>i
                C(i)=((dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %superdiagonal
            elseif i>j
                A(i)=((-dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %sub diagonal 
            elseif i==j
                B(i)=1+((dt*UOLD(i,j))/(2*dx))+(dt/(dy^2));     %main diagonal
            end
        end
    end
    dt=0.2+dt;
end

4 个评论
显示 2更早的评论隐藏 2更早的评论

Dyuman Joshi 2023-3-14

在 MATLAB Online 中打开

Is this what you are looking for?

xmax=1; ymax=7; m=20; n=29; tmax=100; nt=500; 
dx=xmax/m; dy=ymax/n; dt=tmax/nt; 
UOLD=zeros(m,n);VOLD=zeros(m,n);
A=zeros([m,m]);
B=A;
C=A;
while dt<tmax
    for j=1:n
        for i=1:m
            if j>i
                C(j-1,j)=((dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %superdiagonal
            elseif i>j
                A(i,i-1)=((-dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %sub diagonal 
            elseif i==j
                B(i,j)=1+((dt*UOLD(i,j))/(2*dx))+(dt/(dy^2));     %main diagonal
            end
        end
    end
dt=0.2+dt;
end
A
A = 20×20
         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0
B
B = 20×20
1.0e+03 *

    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0
C
C = 28×29
         0 -856.4469         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 -856.4469         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 -856.4469         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 -856.4469         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 -856.4469         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 -856.4469         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 -856.4469         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 -856.4469         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 -856.4469         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 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0

Dyuman Joshi 2023-3-14

"You changing that matrix size only."

How else are you going to get the values on diagonals?

What are the expected outputs?

Dyuman Joshi 2023-3-15

I didn't understand what you meant by your comment below my response.

Also, you did not answer my questions - How else are you going to get the values on "diagonals"?

What are the expected outputs? Please provide exactly what the values of A, B and C you want to get.

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请先登录，再回答此问题。

Answer 1

Dyuman Joshi 2023-3-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1928275-how-to-change-diagonal-subdiagonal-and-superdiagonal-values-with-respect-time-while-using-loop-and#answer_1193390

编辑：Dyuman Joshi 2023-3-15

在 MATLAB Online 中打开

xmax=1; ymax=7; m=20; n=29; tmax=100; nt=500; 
dx=xmax/m; dy=ymax/n; dt=tmax/nt; 
UOLD=zeros(m,n);VOLD=zeros(m,n);
A=zeros(m,m);
B=A;
C=A;
while dt<tmax
    for j=1:n
        for i=1:m
            if j>i
                C(j-1,j)=((dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %superdiagonal
            elseif i>j
                A(i,i-1)=((-dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %sub diagonal 
            elseif i==j
                B(i,j)=1+((dt*UOLD(i,j))/(2*dx))+(dt/(dy^2));     %main diagonal
            end
        end
        dt=0.2+dt;
    end
end
A
A = 20×20
         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
 -847.8653         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0 -849.5816         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0 -851.2980         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0 -853.0143         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0 -854.7306         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0 -858.1633         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0 -859.8796         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0         0 -861.5959         0         0         0         0         0         0         0         0         0         0         0
B
B = 20×20
1.0e+03 *

    1.6967         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0    1.7002         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0    1.7036         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0    1.7070         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0    1.7105         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0    1.7173         0         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0    1.7208         0         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0         0    1.7242         0         0         0         0         0         0         0         0         0         0         0
         0         0         0         0         0         0         0         0         0    1.7276         0         0         0         0         0         0         0         0         0         0
C
C = 28×29
         0 -849.5816         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 -851.2980         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 -853.0143         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 -854.7306         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 -856.4469         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 -858.1633         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 -859.8796         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 -861.5959         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 -863.3122         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 -865.0286         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Dyuman Joshi 2023-3-15

So you need A, B, C and D to be vectors for executing the function TriDiag?

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Answer 2

Oguz Kaan Hancioglu 2023-3-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1928275-how-to-change-diagonal-subdiagonal-and-superdiagonal-values-with-respect-time-while-using-loop-and#answer_1193375

在 MATLAB Online 中打开

As @Dyuman Joshi mentioned, the problem statement is not clear. However vectors don't have diagonal. Please change the A,B, and C as a matrix and use correct indeces. I think it solves your problem.

xmax=1; ymax=7; m=20; n=29; tmax=100; nt=500; 
dx=xmax/m; dy=ymax/n; dt=tmax/nt; 
UOLD=zeros(m,n);VOLD=zeros(m,n);
A=zeros([m,n]);
B=A;
C=A;
while dt<tmax
    for j=1:n
        for i=1:m
            if j>i
                C(i,j)=((dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %superdiagonal
            elseif i>j
                A(i,j)=((-dt*VOLD(i,j))/(4*dy))-(dt/(2*(dy^2)));  %sub diagonal 
            elseif i==j
                B(i,j)=1+((dt*UOLD(i,j))/(2*dx))+(dt/(dy^2));     %main diagonal
            end
        end
    end
    dt=0.2+dt;
end
A
A = 20×29
         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
 -856.4469         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
 -856.4469 -856.4469         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
 -856.4469 -856.4469 -856.4469         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
 -856.4469 -856.4469 -856.4469 -856.4469         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
 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
B
B = 20×29
1.0e+03 *

    1.7139         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    1.7139         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    1.7139         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    1.7139         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    1.7139         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    1.7139         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    1.7139         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    1.7139         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    1.7139         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    1.7139         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0         0
C
C = 20×29
         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0         0         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0         0         0         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0         0         0         0         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469
         0         0         0         0         0         0         0         0         0         0 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469 -856.4469