David wrote:

> That’s probably the right thing to do, particularly given the other parts of the El Nino series, but just checking that you’re aware that you can also develop some ideas about correlation using the following...

Thanks! I'd never really thought of correlations that way, though I know and love the formula you used: it's a Jedi math trick for getting ahold of arbitrary inner products when all you know is inner products of stuff with _itself_.

I'll add this approach as an "appendix".