Backtracking

Though over the past year, the indices I've worked with seem to all have a dominant period of 128 days, this period may not hold true for a longer period of time. After all, markets as a whole also undergo trends. Keeping this in mind, let's take a look at what happens when I analyze the 5 year historical price data of the Nasdaq Composite index...

As before, here's the graph of its prices, this time spanning a greater length of time:

And the graph of its frequency content:

But instead of getting a period of 128 days, the period of this data is actually closer to 341 days. Hmmm...