Numerator and denominator input syntax of matlab control system : (num,den)

Question

I have seen the following form of writing in many matlab routines：

for example, I have a system function

num=1;
den=[1 0 0];
sys=tf(num,den)

If I want to show the step response, or bode plot, I just type

step(sys);
bode(sys);

This I understand.

But I also see another form of writing：

step(num,den);
bode(num,den);

This is an example of stem(num,den)

This is another example of bode2(num,den)

The question is, for the second form, what is the definition of this syntax? I haven't found any detailed explanation of it. I mean, can we use (num,den) to replace sys=tf(num,den)? If so, where can I find some official explanation? Please help! Thanks.

Answer 1

The code you use as an example is written in 1994. This syntax is no longer in use.

Try using the current versions of step and bode.