Very simple customizable inline function to draw arrows. Lightweight and fast for drawing many, many arrows. You customize fill color, linewidth, etc... Tune theta up if you want a wider arrowhead.
takes two [x y] coords and one double, headsize, that allows you to tune the length of the arrowhead to your liking. It's normally set to (length of the line) / 2.5, the headsize variable acts as a multiplier of that (in the numerator).
made this in just a few minutes because the other arrow.m thing is too unwieldy and slow. Enjoy!