Clear Filters
Clear Filters

Modify matrix for partial plot

10 views (last 30 days)
jojo
jojo on 9 May 2020
Commented: Walter Roberson on 9 May 2020
How can I modify the for loops to create a bracket-shaped domain? In otherwords, I would like to plot everything and omit the first quadrant. Thank you!
clear; close all; clc
n = 40;
x = linspace(0,8,n); dx = x(2)-x(1); y = x; dy = dx;
U = zeros(n);
U(n,1:n/2) =10;
U(n/2,n/2:n-1) =0;
U(1,1:n-1) = 10;
U(2:n,n/2) = 0;
U(1:n/2,n) = 7;
U(n/2:n,n/2) = 0;
alpha=1;
ddt = 1/(4*(1/dx^2+1/dy^2));
for w=1:1000
V = U;
for i = 2:n/2-1
for j = 2:n-1
U(i,j) =ddt*((V(i+1,j)-2*V(i,j)+V(i-1,j))/dx^2+ (V(i,j+1)-V(i,j)+V(i,j-1))/dy^2)+ V(i,j);
end
end
end
figure(1)
contour(y,x,U)
figure(2)
surf(y,x,U)
  5 Comments
Walter Roberson
Walter Roberson on 9 May 2020
surf(y, x, Uc)
The 'edgecolor', 'none' just controls drawing the edges of each face. When you have many faces, the edges start to take over the visual impression, because the edges are constant width even when the faces get small.
Walter Roberson
Walter Roberson on 9 May 2020
x and y are both increasing, and you are using x for rows and y for columns. Which is the "first quadrant" ?
(x=0,y=0) (x=0,y=4) (x=0,y=8)
A B
(x=4,y=0) (x=4,y=4) (x=4,y=8)
C D
(x=8,y=0) (x=8,y=4) (x=8,y=8)

Sign in to comment.

Accepted Answer

darova
darova on 9 May 2020
Edited: darova on 9 May 2020
Here are your bourndary conditions
n = 40;
x = linspace(0,8,n); dx = x(2)-x(1); y = x; dy = dx;
U = zeros(n);
U(n,1:n/2) =10;
U(n/2,n/2:n-1) =0+10;
U(1,1:n-1) = 10;
U(2:n,n/2) = 0+10;
U(1:n/2,n) = 7+3;
U(n/2:n,n/2) = 0+10;
alpha=1;
ddt = 1/(4*(1/dx^2+1/dy^2));
h = imagesc(U);
view(2)
Something is missing
I made some changes to your script. It still doesn't work
  2 Comments
jojo
jojo on 9 May 2020
Thanks for the effort. I'm just trying to blank out a section of the plot using for loops (actual computation) instead of plotting using 'none'
darova
darova on 9 May 2020
I did everything i can

Sign in to comment.

More Answers (0)

Community Treasure Hunt

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

Start Hunting!