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

6 vues (au cours des 30 derniers jours)
LightFury Yeji
LightFury Yeji le 7 Fév 2021
Commenté : LightFury Yeji le 7 Fév 2021
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

Réponses (1)

Walter Roberson
Walter Roberson le 7 Fév 2021
%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
  3 commentaires
Walter Roberson
Walter Roberson le 7 Fév 2021
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
LightFury Yeji
LightFury Yeji le 7 Fév 2021
Oh, thank you so much!

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