Surf a function with different values
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I'm trying to surf a function f that takes 2 values: 1 if (x,y) is in A and 2 if (x,y) is in B. How can I do that? I attach also a drawing for x,y.
采纳的回答
Torsten
2023-5-21
Define the function as
f = @(x,y) (y>=2*x) + 2*(y<2*x);
and make a surface plot.
17 个评论
Alexandra Roxana
2023-5-21
编辑：Alexandra Roxana
2023-5-21
The function has exactly the values you want:
f = @(x,y) (y>=2*x) + 2*(y<2*x);
f(0,1)
f(1,0)
But I admit: Defining a function with prescribed values on each triangle of a triangulation will soon become a hard job. And I really don't understand what it should be good for ...
Alexandra Roxana
2023-5-21
Alexandra Roxana
2023-5-21
Alexandra Roxana
2023-5-21
编辑：Alexandra Roxana
2023-5-21
Long story short: I want to calculate the pressure on each triangle from the red domain. The left-hand side of the formula is the pressure on each triangle; the right-hand side is the sum of values of each node from the triangle. The thing is the pressure is constant on each triangle and it has to look like that in the surf. Before it looked like a continuous function which isn't right. And I wanted at first to begin with a simple example.
f = @(x,y) (y>=2*x) + 2*(y<2*x);
x = linspace(0,1,100);
y = linspace(0,2,100);
[X,Y] = ndgrid(x,y);
surf(X,Y,f(X,Y))
shading interp
colorbar
Alexandra Roxana
2023-5-22
Star Strider
2023-5-22
Or:
f = @(x,y) (y>=2*x) + 2*(y<2*x);
x = linspace(0,1,100);
y = linspace(0,2,100);
[X,Y] = ndgrid(x,y);
contourf(X,Y,f(X,Y))
colorbar
Alexandra Roxana
2023-5-22
Alexandra Roxana
2023-5-22
Alexandra Roxana
2023-5-22
The marked part must not appear
You might want to play with this representation:
x1 = [0,0,1];
y1 = [0,2,2];
z1 = [1,1,1];
x2 = [0,1,1];
y2 = [0,0,2];
z2 = [2,2,2];
hold on
s1 = fill3(x1,y1,z1,'r');
s2 = fill3(x2,y2,z2,'b');
hold off
view(25,45)
zlim ([0 3])
rotate(s1,[0 0 1],180)
rotate(s2,[0 0 1],180)
Alexandra Roxana
2023-5-23
编辑：Alexandra Roxana
2023-5-23
Unfortunately that's not going to help me very much because I want to go further and do the same thing but with more triangles like in this case and in each triangle the function to have a different value:
Alexandra Roxana
2023-5-23
编辑：Alexandra Roxana
2023-5-23
Alexandra Roxana
2023-5-27
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