I only need to display the first 11 rows of the answer

Question

LightFury Yeji 2021-2-7

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/738447-i-only-need-to-display-the-first-11-rows-of-the-answer

评论： LightFury Yeji 2021-2-7

在 MATLAB Online 中打开

My program displays an output with so many rows, but I only need the first 11. How do i solve this? Please help

This is the output (and not everything is shown because there are a lot of rows):

This is the desired output:

0.1 0.1 0.0

0.2 0.1 0.5877852523

0.3 0.1 0.8090169944

0.4 0.1 0.9510565163

0.5 0.1 1.0

0.6 0.1 0.9510565163

0.7 0.1 0.8090169944

0.8 0.1 0.5877852523

0.9 0.1 0.3090169944

1.0 0.1 0.0

This is my program:

l=1; %endpoint    
T=1; %maximum time 
alpha = 2; %constant 
m=10; 
N=20;
syms f(x) g(x,t)
f(x)=sin(pi*x);
g(x)=(sin(pi*x))*(cos(2*pi*t));
%STEP1
h=l/m;
k=T/N;
lambda=k*alpha/h;
%STEP2
wij = zeros(m,N,'sym');
for j=2:N
    wij(1,j)=0; %wij(0,j)
    wij(m,j)=0;
end
%STEP3
wij(1,1)=f(0); %wij(0,0)
wij(m,1)=f(l); 
%STEP4
for i=2:m-1
    wij(i,1)=subs(f(x),x,(i*h)); %wij(i,0)
    wij(i,2)=(1-lambda^2)*(subs(f(x),x,(i*h)))+(lambda^2/2)*(subs(f(x),x,((i+1)*h)))+(subs(f(x),x,((i-1)*h)))+k*(subs(g(x),x,(i*h)));
end
%STEP5
for j=2:N-1
    for i=2:m-1
        wij(i,j+1)=2*(1-lambda^2)*wij(i,j)+lambda^2*(wij(i+1,j)+wij(i-1,j))-wij(i,j-1);
    end
end
%STEP6
for j=1:N
    t=j*k;
    for i=1:m
        x=i*h;
        fprintf( '%.1f  %.1f  %s\n',x, t, char(vpa(wij(i,j),10)));
    end
end

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Answer 1

Walter Roberson 2021-2-7

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在 MATLAB Online 中打开

%STEP6
stopping_loop = false;
for j=1:N
    t=j*k;
    for i=1:m
        x=i*h;
        if ~isempty(symvar(wij(i,j))
            stopping_loop = true;
            break;
        end
        fprintf( '%.1f  %.1f  %.10f\n',x, t, double(wij(i,j)));
    end
    if stopping_loop; break; end
end

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Walter Roberson 2021-2-7

在 MATLAB Online 中打开

l=1; %endpoint    
T=1; %maximum time 
alpha = 2; %constant 
m=10; 
N=20;
syms f(x) g(x,t)
f(x)=sin(pi*x);
g(x)=(sin(pi*x))*(cos(2*pi*t));
%STEP1
h=l/m;
k=T/N;
lambda=k*alpha/h;
%STEP2
wij = zeros(m,N,'sym');
for j=2:N
    wij(1,j)=0; %wij(0,j)
    wij(m,j)=0;
end
%STEP3
wij(1,1)=f(0); %wij(0,0)
wij(m,1)=f(l); 
%STEP4
for i=2:m-1
    wij(i,1)=subs(f(x),x,(i*h)); %wij(i,0)
    wij(i,2)=(1-lambda^2)*(subs(f(x),x,(i*h)))+(lambda^2/2)*(subs(f(x),x,((i+1)*h)))+(subs(f(x),x,((i-1)*h)))+k*(subs(g(x),x,(i*h)));
end
%STEP5
for j=2:N-1
    for i=2:m-1
        wij(i,j+1)=2*(1-lambda^2)*wij(i,j)+lambda^2*(wij(i+1,j)+wij(i-1,j))-wij(i,j-1);
    end
end
%STEP6
stopping_loop = false;
for j=1:N
    t=j*k;
    for i=1:m
        x=i*h;
        if ~isempty(symvar(wij(i,j)))
            stopping_loop = true;
            break;
        end
        fprintf( '%.1f  %.1f  %.10f\n',x, t, double(wij(i,j)));
    end
    if stopping_loop; break; end
end
0.1  0.1  0.0000000000
0.2  0.1  0.5877852523
0.3  0.1  0.8090169944
0.4  0.1  0.9510565163
0.5  0.1  1.0000000000
0.6  0.1  0.9510565163
0.7  0.1  0.8090169944
0.8  0.1  0.5877852523
0.9  0.1  0.3090169944
1.0  0.1  0.0000000000
0.1  0.1  0.0000000000