Challenging code problem, advanced matlab code debugger needed.

Here is the current code I am running for a assignment and I can't figure out why my beta term and plot are graphing at zero. The beta isnt actually zero just numbers that are really really small and might as well be condiered zero. That portion of my final graph that shows up should look like something like the other two lines on the graph. If someone could review my code and try and figure out why that cyan line on my graph, or the beta portion keeps graphing at zero it would be much appreciated. Also if you have any ideas as to how and make the code more effecient or run quicker that would be appreciated as well.

Code

[John D'Errico]

Nope. No can do. This is where you need to learn to step through your code, line by line if needed.

You have not even supplied the data that this code uses, so exactly how will we know what it is doing wrong?