I tried to solve 6 couple differential equation, and getting an error which is " Index exceeds the number of array elements. Index must not exceed 2."
1 view (last 30 days)
Show older comments
SAHIL SAHOO
on 2 Jul 2022
Answered: Walter Roberson
on 2 Jul 2022
%how to remove this error " Index exceeds the number of array elements. Index must not exceed 2."
close all;
clc;
format long;
I1 = 0.2
I2 = 0.8
o = 3;
tc = 30E-9;
tf = 230E-6;
a1 = 0.1;
a2 =0.1;
P1 = 0.2;
P2 =0.2;
k= 0.17;
f=@(t,y) [(1/tc).*(y(3)- a1).*y(1)+(k./tc).*y(2).*cos(y(5));
(1/tc).*(y(4)- a2).*y(1)+(k./tc).*y(1).*cos(y(5)) ;
(1/tf).*(P1 - y(3).*(I1+1));
(1/tf).*(P2 - y(4).*(I2+1));
o - (k./tc).*((y(1)./y(2)) + (y(1)./y(2))).*sin(y(5))
];
[x,y]=runge_kutta_4(f,[0,5],[1,1,1,1,1],0.1);
plot(x,y);
title('When Time Step is 0.1');
legend('x(t)', 'y(t)', 'z(t)', 'Location', 'NorthEast')
xlabel('t')
ylabel('Solutions')
figure;
hold on;
for h=[0.1, 10^-3, 10^-6]
[x,y]=runge_kutta_4(f,[0,5],[1,1,1,1,1],h);
plot(x,y(:,1));
end
title('Plot of x(t) for 3 Different Time Steps');
xlabel('t')
ylabel('x(t)')
function [x,y]=runge_kutta_4(f,tspan,y0,h)
x = tspan(1):h:tspan(6);
y = zeros(length(x),5);
y(1,:) = y0;
for i=1:(length(x)-1)
k_1 = f(x(i),y(i,:));
k_2 = f(x(i)+0.5*h,y(i,:)+0.5*h*k_1);
k_3 = f((x(i)+0.5*h),(y(i,:)+0.5*h*k_2));
k_4 = f((x(i)+h),(y(i,:)+k_3*h));
y(i+1,:) = y(i,:) + (1/6)*(k_1+2*k_2+2*k_3+k_4)*h;
end
end
0 Comments
Accepted Answer
Walter Roberson
on 2 Jul 2022
x = tspan(1):h:tspan(6);
That line is expecting that tspan is a vector or array with at least 6 elements
Working backwards
function [x,y]=runge_kutta_4(f,tspan,y0,h)
tspan is coming from the second parameter of the call
[x,y]=runge_kutta_4(f,[0,5],[1,1,1,1,1],h);
which is [0,5] -- which only has two elements, not at least 6.
0 Comments
More Answers (0)
See Also
Categories
Find more on Ordinary Differential Equations in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!