Out of memory error message when attempting to plot in 3D

Hi all,

From my following code as I'm trying to plot the trajectory of 3 bugs in three dimensions I am presented with the folllowing error message:

Out of memory. The likely cause is an infinite recursion within the program.

Error in bugs>g (line 37) dxdt=g(t,f)

From my following code:

clc, clear, clear all

ti=0;
tf=1000;
tspan= linspace(ti,tf,1000000);
f0 = [0; 0; 0; 1; 2; 0; 1; 0; 3; 0; 2; 3];
[t, f] = ode45(@g, tspan, f0);

%Trajectories are done in 3 coordinates x,y,z
i_1=(f(:,1)); %Trajectory of bug 1
j_1=(f(:,2));
k_1=(f(:,3));

i_2=(f(:,4)); %Trajectory of bug 2
j_2=(f(:,5));
k_2=(f(:,6));

i_3=(f(:,7)); %Trajectory of bug 3
j_3=(f(:,8));
k_3=(f(:,9));

i_4=(f(:,10));
j_4=(f(:,11));
k_4=(f(:,12));
figure
hold on
plot3(i_1, j_1, k_1, tspan)
plot3(i_2, j_2, k_2, tspan)
plot3(i_3, j_3, k_3, tspan)
plot3(i_4, j_4, k_4, tspan)
title('test')
xlabel('x')
ylabel('y')
zlabel('z')

function dxdt = g(t,f)
dxdt=g(t,f)
dxdt=[(f(2)-f(1))/(sqrt((f(2)-f(1))^2+(f(6)-f(5))^2+(f(10)-f(9))^2));
    (f(6)-f(5))/(sqrt((f(2)-f(1))^2+(f(6)-f(5))^2+(f(10)-f(9))^2));
    (f(10)-f(9))/(sqrt((f(2)-f(1))^2+(f(6)-f(5))^2+(f(10)-f(9))^2));
    (f(3)-f(2))/(sqrt((f(3)-f(2))^2+(f(7)-f(6))^2+(f(11)-f(10))^2));
    (f(7)-f(6))/(sqrt((f(3)-f(2))^2+(f(7)-f(6))^2+(f(11)-f(10))^2));
    (f(11)-f(10))/(sqrt((f(3)-f(2))^2+(f(7)-f(6))^2+(f(11)-f(10))^2));
    (f(4)-f(3))/(sqrt((f(4)-f(3))^2+(f(8)-f(7))^2+((f12)-f(11))^2));
    (f(8)-f(7))/(sqrt((f(4)-f(3))^2+(f(8)-f(7))^2+(f(12)-f(11))^2));
    (f(12)-f(11))/(sqrt((f(4)-f(3))^2+(f(8)-f(7))^2+(f(12)-f(11))^2));
    (f(1)-f(4))/(sqrt((f(1)-f(4))^2+(f(5)-f(8))^2+(f(9)-f(12))^2));
    (f(5)-f(8))/(sqrt((f(5)-f(8))^2+(f(1)-f(4))^2+(f(9)-f(12))^2));
    (f(9)-f(12))/(sqrt((f(1)-f(4))^2+(f(5)-f(8))^2+(f(9)-f(12))^2))];
end

Thanks.

Answer 1

[Jan]

function dxdt = g(t,f)
dxdt=g(t,f)
...
end

This function calls itself recursively. Of course this let Matlab crash. What is the purpose of "dxdt=g(t,f)"? Simply delete this line to solve this problem.

The code block does not look smart. Compare:

dxdt=[(f(2)-f(1))/(sqrt((f(2)-f(1))^2+(f(6)-f(5))^2+(f(10)-f(9))^2));
    (f(6)-f(5))/(sqrt((f(2)-f(1))^2+(f(6)-f(5))^2+(f(10)-f(9))^2));
    (f(10)-f(9))/(sqrt((f(2)-f(1))^2+(f(6)-f(5))^2+(f(10)-f(9))^2));
    (f(3)-f(2))/(sqrt((f(3)-f(2))^2+(f(7)-f(6))^2+(f(11)-f(10))^2));
    (f(7)-f(6))/(sqrt((f(3)-f(2))^2+(f(7)-f(6))^2+(f(11)-f(10))^2));
    (f(11)-f(10))/(sqrt((f(3)-f(2))^2+(f(7)-f(6))^2+(f(11)-f(10))^2));
    (f(4)-f(3))/(sqrt((f(4)-f(3))^2+(f(8)-f(7))^2+(f(12)-f(11))^2));   % BUG: f12->f(12)
    (f(8)-f(7))/(sqrt((f(4)-f(3))^2+(f(8)-f(7))^2+(f(12)-f(11))^2));
    (f(12)-f(11))/(sqrt((f(4)-f(3))^2+(f(8)-f(7))^2+(f(12)-f(11))^2));
    (f(1)-f(4))/(sqrt((f(1)-f(4))^2+(f(5)-f(8))^2+(f(9)-f(12))^2));
    (f(5)-f(8))/(sqrt((f(5)-f(8))^2+(f(1)-f(4))^2+(f(9)-f(12))^2));
    (f(9)-f(12))/(sqrt((f(1)-f(4))^2+(f(5)-f(8))^2+(f(9)-f(12))^2))];

With:

a = sqrt((f(2)-f(1))^2 + (f(6)-f(5))^2 + (f(10)-f(9))^2);
b = sqrt((f(3)-f(2))^2 + (f(7)-f(6))^2 + (f(11)-f(10))^2);
c = sqrt((f(4)-f(3))^2 + (f(8)-f(7))^2 + (f(12)-f(11))^2);
d = sqrt((f(1)-f(4))^2 + (f(5)-f(8))^2 + (f(9) -f(12))^2);

dxdt = [ ...
    (f(2)  - f(1))  / a;
    (f(6)  - f(5))  / a;
    (f(10) - f(9))  / a;
    (f(3)  - f(2))  / b;
    (f(7)  - f(6))  / b;
    (f(11) - f(10)) / b;
    (f(4)  - f(3))  / c;
    (f(8)  - f(7))  / c;
    (f(12) - f(11)) / c;
    (f(1)  - f(4))  / d;
    (f(5)  - f(8))  / d;
    (f(9)  - f(12)) / d];

This is even faster.