problem with plotting a 1D graph

Question

Yamina chbak 2020-12-1

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/671998-problem-with-plotting-a-1d-graph

评论： Yamina chbak 2020-12-3

Hi,

I have solved a 2D time problem U(x,y,t), 0<=x,y<=L and 0<=t<=T, by FEM and i get

trisurf(TRI,x,y,U(:,N))  % N number of time steps
% TRI triangle for create mesh

My question is how to write Matab code to see plot 1D for U solution of this problem if I choose for example : U(5,6,t) for all 0<=t<=T and U(x,5,0.15) for 0<=x<=L.

(To simulate 1D problem through a 2D problem ) this what i try write plot but it is not correct

%  plot of time : U(5,6,t)
t=linspace(0,2,0.15);
for i=1:np   % np number of nodes
find(x(m)==5 & y(m)==6)
end
plot(t,U(:,t))
%%%%%%%%%%%%%
% plot of x : U(x,5,0.15)
t=0.15; 
for i=1:np % np numbers of nodes
find(y(m)==5
end
plot(x,U(:,t)

Please i need help

Thanks

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Answer 1

Stephan 2020-12-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/671998-problem-with-plotting-a-1d-graph#answer_562608

编辑：Stephan 2020-12-2

在 MATLAB Online 中打开

You dont save the results of find anywhere - try:

%  plot of time : U(5,6,t)
t=linspace(0,2,0.15);
for i=1:np   % np number of nodes
U(i,:) = find(x(m)==5 & y(m)==6)
end
plot(t,U)

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Yamina chbak 2020-12-3

在 MATLAB Online 中打开

Thanks @Stephan for answer my question, but i think i give you my mistaken information.

Look my code what i did it for solving 2d problem and see plot2D :

% i have a list of Nodes
x=Nodes(:,2); y=Nodes(:,3);
np=size(x,1);  %number of nodes
T=1;N=21; dt=T/N-1;
for k=1:N
 t(k)=(k-1)*dt;
    L(:,k+1)=g(x,y,t(k+1))  % a simple function dependant time
b(:)=M+L(:,k+1);      % M is a matrix
% solver problem
U(:,k+1)=A\b(:);
end
% Resultat 
figure()
trisurf(TRI,x,y,U(:,N))