how to finde state estimation error?

I used ode command to find actual states of differential equation as this?

[t,x]= ode45(@exam3f,[Initial_Time Final_Time], [0.01 0.5 0.01 0.5 0.01 0.5 1] );

and the estimated states are

[t1,x3]= ode45(@exam6f,[Initial_Time Final_Time], [0.01 0.5 0.01 0.5 0.01 0.5 1] );

when i want to find error between actual and estimated states

error= x-x3;

it gives an error dimensions not same.