Re: Hello, I am david
Hi David, its worth pointing out as above that Aikido is many years of training to get to the goal you are looking for which it will do very well. Yet in terms of tactical awareness and defence against being mugged, Krav Maga (which incorporates elements of Aikido) may be worth a look also as you train in Aikido.
Its also worth listening to the truth which is that the best defence against a knife irrespective of how good you think you are may be to run, using techniques against a Knife is something to put much time and effort into thinking about, The reality of it is not like on TV!
The Book, "Aikido for Life" by Gaku Homma is a very good one to get started with to understand what Aikido is about and how long it takes and what its processes are and so forth for a beginner.
Good luck with it anyway, I am sure you will do well!