 Let's take a look at TXTOUT(O_BPF) to see filtered output.  This is what 0.0333Hz is!! This wave was hidden in the chart but we have
picked it up by a Band Pass Filter.  You can change the scale by "View" -> "Scale Change"
and check this wave's one period is 30 days.  That's it for this class. FFT is very strong tool to analyze a series of data. Digital Filter is also very strong tool to remove unnecessary information and even to pick up some hidden information.
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