Interesting. A quick look at the code, at least for the case where an output argument is specified, shows that the function that parses the inputs to lsim() doesn't enforce that the first argument(s) in the list must be a dynamic system object. In fact, I don't think it enforces any order other than that u comes before t, and t comes before x0.
For example:
sys = tf(1,[1 1]);
t = 0:10;
u = rand(size(t));
method = 'foh';
y1 = lsim(sys,u,t,method);
y2 = lsim(method,u,sys,t);
isequal(y1,y2)
Not sure TMW would consider this a bug. Certainly undocumented behavior.
Did it cause a problem or just asking out of curiosity?
