You use
F = @(t,r) 1/(50*Power(t,2));
Power appears to be undefined in the code you gave. Perhaps you are thinking of power
Your F function takes t (presumably time) as the first variable and r (unknown purpose) as its second column, and it ignores the second parameter. But you are invoking
k1 = F(y(:,i),t(i));
in which you appear to be passing y as the first parameter and a time as the second parameter. That k1 y(:,i) is going to be received into the parameter that F knows as t, and that k1 t(i) is going to be received into the parameter that F knows as r (where it is going to be ignored).
For the sake of the readers, you need to be consistent about whether it is your first parameter or the second parameter of F that is the time parameter.
