Matlab code wont disply the figure 2

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Bijaya 2023-10-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2032734-matlab-code-wont-disply-the-figure-2

评论： Dyuman Joshi 2023-10-13

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

c= 1; % unit conversion

L=1; % t=[L]/[c]

C=0.1;

N=1000;

Np=N+1;

dx= L/N;

x=(0:dx:L)';

dt=C*dx/c;

sqrC=C*C;

% step2 convert PDE to linear algebraic equations

A= sparse(Np,Np); % matrix creation as rows,columns

u= zeros(Np,1); % unknowns

b= zeros(Np,1); %RHS

% generate a wave function

u = sin(3*pi*x);

%figure(1);clf;hold on

plot(x,u,'-b','Linewidth',L);

xlabel('x([L])')

ylabel('Amplitude([L])');

title('Intial Wave')

set(gca,'Linewidth',1,'fontsize',12)

box on;

ylim([-1,1]);

uset{1} = u; % future

uset{2} = u; % present

uset{3} = u; % previous

uset{4} = u; % previusly previous

% Apply boundary conditions

A(1,1)= 1; b(1)= 0;

A(Np,Np) = 1; b(Np) = 0;

for i= 2:Np-1

A(i,i) =2 +sqrC*2;

A(i,i-1) = -sqrC;

A(i,i+1) = -sqrC;

b(i) =5*uset{1}(i) - 4*uset{2}(i) + uset{3}(i);

end

%u=A/b

%uset{1}=u;

t=0;

Nt=100000;

for k=0:Nt

t= t+dt;

for i=2:Np-1

b(i) =5*uset{1}(i) - 4*uset{2}(i) + uset{3}(i);

end

u=A\b;

uset{3}=uset{2};

uset{2}= uset{1};

uset{1}=u;

end

if k==1

figure(2); clf; hold on;

xlabel('x')

ylabel('y','amplitude')

set(gca,'Linewidth',1,'fontsize',12)

box on

h=1;

ylim([-1,1])

end

if mod(k,50)==0

% figure(2);

if h~=0; delete(h); end

h = plot(x,u, '-b', 'Linewidth', 2);

title(['Time:' num2str(t)]);

end

Unrecognized function or variable 'h'.

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Answer 1

Walter Roberson 2023-10-13

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https://ww2.mathworks.cn/matlabcentral/answers/2032734-matlab-code-wont-disply-the-figure-2#answer_1332074

在 MATLAB Online 中打开

h is not initialized so you cannot test

if h~=0; delete(h); end

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Bijaya 2023-10-13

移动：Dyuman Joshi 2023-10-13

I have already defined h=1; BUT it still keep on giving same error . How do i fix it ?

Dyuman Joshi 2023-10-13

No, that statement is subjected to a condition i.e. k==1. And as the condition is not satisfied (because the value of k is Nt), h=1 is not executed.

You can directly over-write h (if it has been defined), there's no need to delete it.

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Matlab code wont disply the figure 2

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