MATLAB Answers

0

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".)

Asked by Riyadh Salim on 11 Nov 2019
Latest activity Edited by James Tursa
on 11 Nov 2019
%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

  1 Comment

What is your question? Where is the error?

Sign in to comment.

1 Answer

Answer by James Tursa
on 11 Nov 2019
Edited by James Tursa
on 11 Nov 2019

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?

  0 Comments

Sign in to comment.