Strawman?

Our discussion here is in reply to the parent who made a claim that the second derivative was useful in finding extrema. I have posted so that future readers will not believe this, as I believe it to be untrue. In reply to my claim you have posted a number interesting things - but none seemingly address the claims of the parent, or myself.

The OP claims that the second derivative is useful for determining extrema. His claim suggests that looking at toggling signs on the resulting series indicates extrema. I claim this as *false*.

I also claim that it is possible to find extrema using the first derivative. Any time the derivative crosses the X axis there will be a maxima or minima present within the source series. I do *not* claim that this will find all extrema - I do claim that it will also require additional processing to capture all extrema of interest. Are you claiming this is false?

Your above program is quite a bit shorter than mine. I have a different type of data, but I am pretty sure that looking at deltas like this is a more precise and efficient way of solving the problem than using first derivatives - I disagree that it's more accurate, but that's nitpicking. Overall it is better than doing solely a first derivative and picking from that.

Finally, I strongly disagree that using inverted graphs (even if that's what's used in computer graphics) is a good way to prove your point about much of anything. That said, had you labelled your graph and explained what it was I we both could have saved some time

In reply to Re^8: Any idea for predicting the peak points in the graph by perl by gaimrox
in thread Any idea for predicting the peak points in the graph by perl by Anonymous Monk

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