Thanks Paul,
This sort of thing is always a balance between completeness and simplicity. I have opted for simplicity. To the best of my knowledge the examples work no matter what rubbish you throw at them. I have deliberately not tried to make universally applicable functions as all the extra code makes it difficult for a newcomer to see the principal message. In that sense I am not expecting anyone to recommend their adoption without reservations.
At the end of my post I referred to the potential problem that the data may be incomplete and provided a link to an example that deals with that problem. I believe it would be counterproductive to deal with that issue in this demo.
Unfortunately as you add (necessary) bells and whistles the examples become more and more specific to a particular case. All I want to achieve with this demo is to point people in the appropriate direction without having to repeat the same stuff over and over in reply to other Threads.
Feel free to add some examples and explanations of your own. It would be convenient to have them all in the same place.
...R