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".)

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Riyadh Salim
Riyadh Salim 2019-11-11
编辑： James Tursa 2019-11-11
%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

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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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