# [SciPy-user] concave and convex function

josef.pktd@gmai... josef.pktd@gmai...
Wed May 27 09:27:25 CDT 2009

```On Wed, May 27, 2009 at 10:13 AM, mudit sharma <mudit_19a@yahoo.com> wrote:
>
> Thanks Robert. I appreciate your response.
>
> I found the solution finally, which is, using Savitzky Golay filter for smoothing as it preserves the shape. Then using peak and trough points detection algorithm. Some useful links here:
> http://terpconnect.umd.edu/~toh/spectrum/PeakFindingandMeasurement.htm. Unfortunately, all these matlab scripts so will have to write python equivalent.
>
> Mudit
>
>
>
> ----- Original Message ----
> From: Robert Kern <robert.kern@gmail.com>
> To: SciPy Users List <scipy-user@scipy.org>
> Sent: Monday, 18 May, 2009 23:20:24
> Subject: Re: [SciPy-user] concave and convex function
>
> On Mon, May 18, 2009 at 02:57, Sebastian Walter
> <sebastian.walter@gmail.com> wrote:
>> On Sun, May 17, 2009 at 3:50 PM, mudit sharma <mudit_19a@yahoo.com> wrote:
>>>
>>>
>>> By M & W curve I meant M & W shape curves( subset ) and by cycle I meant wave cycle.
>> Is that supposed to describe what is meant by M & W?
>
> Peak-trough-peak and trough-peak-trough patterns, respectively, like
> the shapes of the letters.
>
>> No offense, but
>> if you want help, you should
>> state your problem in a way that other ppl understand....
>
> His actual question is reasonably well-worded (he wants to classify
> the signal into convex and concave portions), but you got distracted
> by the irrelevant portion.
>
> --

I still don't see identifying peaks and troughs anywhere in the
initial question.
Identifying peaks and troughs is a question for zeros in the first
derivative; identifying convex and concave regions is a question for
zeros in the second derivative.

There is an entire "industry" trying to do this for the business cycle.

Josef
```