Ah, ok, I understand your reasoning better. That's a great point, and one I wholeheartedly support for web development and application programming in general :) 

I think for scientific programming, though, it's *really* important to be able to perform a computation and then easily display the result; it doesn't matter so much about the specifics of how it looks (e.g. color), just that you can easily take a look at the result (if you wanted to actually plot the algorithm as a figure for a paper, for example, then you probably would want to write your own plotting code from scratch anyway). And, because the plotting methods for algorithms like this one tend to be quite specific to the algorithm itself, you unfortunately can't usually reuse much of the code. So, moving the plotting code somewhere else mostly just adds an extra overhead cost of figuring out where the function is you need to call to actually display it.

This is probably a good discussion to have in the text, though, so I'll try to flesh out my opinions on this more in the README.