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

2023 3 14
2 个回答
回答已采纳
更新时间：2023 4 29
6 次查看（30 天）

0 个投票

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
Dyuman Joshi 2023-3-14
Ran in:
Ran in:
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
Yanni
Yanni 2023-3-14
You changing that matrix size only. but i need distinct main daigonal values and other two as well. here, main diagonal values are same. so, how to get distinct values with respect to time?
Dyuman Joshi
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
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.

请先登录，再进行评论。

请先登录，再回答此问题。

 采纳的回答

Dyuman Joshi
Dyuman Joshi 2023-3-15
编辑：Dyuman Joshi 2023-3-15
Ran in:

0 个投票

Ran in:
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

更多回答（1 个）

Ran in:

0 个投票

Ran in:
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

类别

在 帮助中心 和 File Exchange 中查找有关 Operating on Diagonal Matrices 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by