[SciPy-user] concave and convex function

Sebastian Walter sebastian.walter@gmail....
Mon May 18 02:57:42 CDT 2009


On Sun, May 17, 2009 at 3:50 PM, mudit sharma <mudit_19a@yahoo.com> wrote:
>
> Thanks for your response.
>
> 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?  No offense, but
if you want help, you should
state your problem in a way that other ppl understand...

>
>
>
>
> ----- Original Message ----
> From: "josef.pktd@gmail.com" <josef.pktd@gmail.com>
> To: SciPy Users List <scipy-user@scipy.org>
> Sent: Sunday, 17 May, 2009 8:32:17
> Subject: Re: [SciPy-user] concave and convex function
>
> On Fri, May 15, 2009 at 9:10 PM, mudit sharma <mudit_19a@yahoo.com> wrote:
>>
>> I have following sample (actual dataset is much bigger):
>>
>> [ 0.48  0.64  0.69  0.67  0.67  0.65  0.68  0.63  0.62  0.61  0.61  0.6
>>  0.58  0.62  0.64  0.63  0.63  0.61  0.60  0.61  0.62  0.65  0.67  0.67
>>  0.67  0.68  0.68  0.66  0.68  0.65  0.65  0.65  0.65  0.64  0.64  0.65
>>  0.65  0.66  0.66  0.64  0.65  0.64  0.68  0.69  0.70   0.69  0.7   0.68
>>  0.64  0.64  0.65  0.67  0.68  0.67  0.67  0.66  0.66  0.64  0.64  0.58
>>  0.53  0.53  0..52]
>>
>>
>> I am looking to scan for all M & W curve formation and cycles. For this I need to detect all concave and convex points on curve. Is there function available in scipy or mlab to fit data into concave and convex function? If there's any other straightforward way to achieve this, pleas suggest.
>>
>
> I'm not sure what you need, I don't know what M & W curve formation
> and cycles are.
>
> But for a 1d array, you can just check the second derivative with
> np.diff, something like
>
> x=np.linspace(0.,5.)
> y = np.sin(x)
> z=np.diff(np.diff(y))>0 # isconvex
> z1=np.diff(y,2) # 2nd derivative
> np.array(z1>0,int) -np.array(z1<0,int) # concave indicator
>
> but your example array has lots of ups and downs. If it is a noisy
> dataset, you might need to smooth it first?
>
> Josef
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