can someone help me to solve this error (This statement is not inside any function. (It follows the END that terminates the definition of the function "RK4".)

11 次查看(过去 30 天)
%task4
function adaptive
close all;
y = [0:0]; T = [0];
h = 0.001;
t = 0; i = 1;
err = 1e-3;
while t < 0.5
e = 1;
%h = 0.01;
while (e > err)
y_1 = y(:,i) + h * f(t, y(:,i));
y_2 = y(:,i) + h/2 * f(t, y(:,i));
y_2 = y_2 + h/2 * f(t+h/2, y_2);
e = 2^1*(norm(y_2 - y_1))/(2^1-1);
if (e > err)
h = 0.9 * h*(err*(2^1-1)/(2^1*(norm(y_2-y_1))));
end
end
y(:,i+1) = y_2;
t = t + h; i = i + 1;
T(i) = t;
if (e < 0.5 * err)
h = h*2;
end
end
end
function euler(i, h, t, ye)
ye(i+1) = ye(i) + h*( f( t(i), ye(i) ) );
end
function impli(i, h, t, y_i)
y_i(i)= yi(i) + h*( f( t(i), yi(i) ) );
yi(i+1)=yi(i) + h*(f(t(i+1),y_i(i)));
end
function Heuns(i, h, t, yh)
yh(i+1) = yh(i)+ h/2 * (f(t(i),yh(i)) + f(t(i+1),(yh(i)+ h*f(t(i),yh(i)))));
end
function RK4(i, h, t, yrk)
k1 = f(t(i), yrk(i));
k2 = f(t(i) + h/2, yrk(i) + h/2*k1);
k3 = f(t(i) + h/2, yrk(i) + h/2*k2);
k4 = f(t(i) + h, yrk(i) + h*k3);
yrk(i+1) = yrk(i) + h/6*(k1 + 2*k2 + 2*k3 + k4);
end
%plot(t,ye, 'b');
%figure;
%plot(t, yi, 'r');
%figure;
%plot(t, yh, 'g');
%figure;
%plot(t, yrk, 'y');
%figure;
plot(t, ye, 'b',t, yi, 'r', t, yh, 'g', t, yrk, 'y',x,Yx);
legend('euler','impli','Heuns','RK4','Real')
%plot(t, ye)
function dy=f(t,y)
d = 10;
dy = -d*(y-(cos(t)));
end

回答(1 个)

James Tursa
James Tursa 2019-11-11
编辑:James Tursa 2019-11-11
Looks like your plot( etc ) and legend( etc ) lines are stuck inbetween two functions. Did you intend them to be inside a script that calls all of your functions?

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