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".)

%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

[darova]

What is your question? Where is the error?

Answer 1

[James Tursa]

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?