# Matlab problem

1. Oct 12, 2011

### bdave

Hello everyone, I'm having a problem.

This is my program:

Script simpode2120.m:
function zdot=simpode2120(t,z)
zdot=[z(2);(20/100)*(50-10*z(2)-30*(z(1)-z(3)));z(4);(1/25)*(-245.2*z(4)-30*(z(1)-z(3))-50*z(3))];
end

Script simpode2140.m:
function wdot=simpode2140(t,w)
wdot=[w(2);(40/100)*(50-10*w(2)-30*(w(1)-w(3)));w(4);(1/25)*(-245.2*w(4)-30*(w(1)-w(3))-50*w(3))];
end

Script simpode2160.m:
function xdot=simpode2160(t,x)
xdot=[x(2);(60/100)*(50-10*x(2)-30*(x(1)-x(3)));x(4);(1/25)*(-245.2*x(4)-30*(x(1)-x(3))-50*x(3))];
end

Script simpode2180.m:
function sdot=simpode2180(t,s)
sdot=[s(2);(80/100)*(50-10*s(2)-30*(s(1)-s(3)));s(4);(1/25)*(-245.2*s(4)-30*(s(1)-s(3))-50*s(3))];
end

Script simpode21100.m:
function bdot=simpode2180(t,b)
bdot=[b(2);(100/100)*(50-10*b(2)-30*(b(1)-b(3)));b(4);(1/25)*(-245.2*b(4)-30*(b(1)-b(3))-50*b(3))];
end

Script Exode21.m:

clear
clc
close all

% Solving ODE:
[t,z]=ode45('simpode2120',[0 100],[0 0 0 0]);
[t,w]=ode45('simpode2140',[0 100],[0 0 0 0]);
[t,x]=ode45('simpode2160',[0 100],[0 0 0 0]);
[t,s]=ode45('simpode2180',[0 100],[0 0 0 0]);
[t,b]=ode45('simpode21100',[0 100],[0 0 0 0]);

% Obtaining x1:
z=z(:,1);
w=w(:,1);
x=x(:,1);
s=s(:,1);
b=b(:,1);

% Obtaining x'1:
z1=z(:,2);
w1=w(:,2);
x1=x(:,2);
s1=s(:,2);
b1=b(:,2);

% Obtaining x2:
z2=z(:,3);
w2=w(:,3);
x2=x(:,3);
s2=s(:,3);
b2=b(:,3);

% Obtaining x'2:
z3=z(:,4);
w3=w(:,4);
x3=x(:,4);
s3=s(:,4);
b3=b(:,4);

% Plot Results:
subplot(2,1,1),plot(t,z, t,w, t,x, t,s, t,b);
grid on
xlabel('Time (s)')
ylabel('x')
title('Values for x1')
legend('x20 ','x40','x60','x80','x100');

subplot(2,1,2),plot(t,z1, t,w1, t,x1, t,s1, t,b1);
grid on
xlabel('Time (s)')
ylabel('x')
title('Values for x1dot')
legend('x20 ','x40','x60','x80','x100');

subplot(2,2,1),plot(t,z2, t,w2, t,x2, t,s2, t,b2);
grid on
xlabel('Time (s)')
ylabel('x')
title('Values for x2')
legend('x20 ','x40','x60','x80','x100');

subplot(2,2,1),plot(t,z3, t,w3, t,x3, t,s, t,b);
grid on
xlabel('Time (s)')
ylabel('x')
title('Values for x2dot')
legend('x20 ','x40','x60','x80','x100');

I keep getting an error of:
??? Attempted to access z(:,2); index out of bounds because size(z)=[1217,1].

Error in ==> Exsimpode21 at 23
z1=z(:,2);

>>

If I just plot that one part, it does it fine. Some of the other variables also bring about the same problem.
How do I fix this?
Thanks