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Can anyone give me a clear example of what a "monotonic nonlinear trend" is? I am trying to teach myself time series analysis and ran across this phrase. I know what a nonlinear trend looks like but what is a monotonous one? How does it differ from a non-monotonous nonlinear trend?

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A monotone trend would be one that is either increasing, like this: increasing

or decreasing, like this: decreasing

The trend below is not monotone. not monotone

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What software did you use to make these? – Eric Stucky Jan 2 '13 at 9:04
@Eric I graphed these functions in Maple 16; they are combinations of polynomial and trig functions picked for illustrative value. – user53153 Jan 2 '13 at 15:45

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