Finding local minima and maxima of a graph

[Bryan McCormick]

Peter, Jonathan

I had thought to use a sin function on the time series to find peak and 
trough values. I would filter the sin function results for those close 
to 1 or -1, though I am not sure what the filter interval will be just yet.

Then, I would be able to grab the value from the actual time series from 
the date array walking the sin function results would produce.

Does this seem like a valid means to do this? In terms of programming it 
would be a breeze, but is it a valid method?