Impz function fast algorithm?

Does anybody here know what is the code algorithm behind the impz function? I know it uses the recursive algorithm but how is such implemented in impz that it can get the impulse response of very high N and M orders (numerator and denominator coefficients)? I can make a script that gets the impulse response of a second order lccde but I want to know a GENERAL code that can get the impulse response of any lccdes regardless of their order.

Answer 1

[Walter Roberson]

I do not see any evidence that impz uses anything recursive.

The algorithm is described at https://www.mathworks.com/help/signal/ref/impz.html#f7-1073402

You can look at the complete code:

type impz

[Riven Yvet]

Thank you! Is there any other way to find the impulse response rather than filter and impz? Can I use freqz?

[Walter Roberson]

Sorry, I am not not familiar enough with signal processing to know.