As phrased, this questions is primarily opinion based, which is off-topic and subject to closure... "How can I improve" does not have a specific end goal. Perhaps you would do better on codereview.stackexchange.com. You can use the
profile
tool in MATLAB to look for your bottlenecks if speed is the aim. You included Monte Carlo in the title but I'm not sure that's related from what you've shown - it's not mentioned again in the question. Please have a think about how this could be improved to be more specific and
edit the question to make it on topic —
Wolfie 7 secs ago