Prev: how do you detect spikes?
Next: Download new programs and english courses
From: TideMan on 11 Jun 2010 17:18
On Jun 12, 7:27 am, Tim Wescott <t...(a)seemywebsite.now> wrote:
> On 06/11/2010 12:05 PM, Luna Moon wrote:
>
>
>
> > On Jun 11, 2:24 pm, Jerry Avins<j...(a)ieee.org>  wrote:
> >> On 6/11/2010 2:13 PM, Luna Moon wrote:
>
> >>> Hi all,
>
> >>> I have signals that are very chaotic and choppy. I suspect that there
> >>> are quite a bunch of major and minor cycles inside. What's the best
> >>> way to detect and single out those cycles?
>
> >> FFT?
>
> >>> Any Matlab code around?
>
> >> Sure!
>
> >> Jerry
> >> --
> >> Engineering is the art of making what you want from things you can get..
>
> > How? I am looking for a complete solution...
>
> There's a reason that 'work' is a dirty four letter word.
>
> FFT, look for significant spikes.  What's "significant" in your case
> will be different from the next guy's -- which is why you have to do the
> work.
>
> --
> Tim Wescott
> Control system and signal processing consultingwww.wescottdesign.com

In ocean wave analysis, we use two approaches:
1. Spectral analysis - "significant wave height" Hs is 4*sqrt(M0),
where M0 is the zeroth moment of the spectrum (i.e. the variance) and
the period is usually taken as the peak of the spectrum (but there are
others).
2. Zero-crossing analysis - split the signal into a series of waves
between zero up-crossings, then sort the waves and calculate the
average of the highest third of the waves, this is Hz. Tz is the
average period of the highest third of the waves.

Hz should be close to Hs or there is something screwy with your
signal.
From: Tim Wescott on 11 Jun 2010 18:19
On 06/11/2010 02:18 PM, TideMan wrote:
> On Jun 12, 7:27 am, Tim Wescott<t...(a)seemywebsite.now> wrote:
>> On 06/11/2010 12:05 PM, Luna Moon wrote:
>>
>>
>>
>>> On Jun 11, 2:24 pm, Jerry Avins<j...(a)ieee.org> wrote:
>>>> On 6/11/2010 2:13 PM, Luna Moon wrote:
>>
>>>>> Hi all,
>>
>>>>> I have signals that are very chaotic and choppy. I suspect that there
>>>>> are quite a bunch of major and minor cycles inside. What's the best
>>>>> way to detect and single out those cycles?
>>
>>>> FFT?
>>
>>>>> Any Matlab code around?
>>
>>>> Sure!
>>
>>>> Jerry
>>>> --
>>>> Engineering is the art of making what you want from things you can get.
>>
>>> How? I am looking for a complete solution...
>>
>> There's a reason that 'work' is a dirty four letter word.
>>
>> FFT, look for significant spikes. What's "significant" in your case
>> will be different from the next guy's -- which is why you have to do the
>> work.
>>
>> --
>> Tim Wescott
>> Control system and signal processing consultingwww.wescottdesign.com
>
> In ocean wave analysis, we use two approaches:
> 1. Spectral analysis - "significant wave height" Hs is 4*sqrt(M0),
> where M0 is the zeroth moment of the spectrum (i.e. the variance) and
> the period is usually taken as the peak of the spectrum (but there are
> others).
> 2. Zero-crossing analysis - split the signal into a series of waves
> between zero up-crossings, then sort the waves and calculate the
> average of the highest third of the waves, this is Hz. Tz is the
> average period of the highest third of the waves.
>
> Hz should be close to Hs or there is something screwy with your
> signal.

Which is an example of a way to do it in a specific domain, that has a
specific probability distribution to the signal.

Other signals (a few simple tones of equal amplitude buried in wideband
noise, for instance) will have other methods that would need to be applied.

Which is why we're all telling the OP that there isn't a prepackaged
solution, unless it's specific to his problem.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
From: Mikolaj on 15 Jun 2010 17:56
Dnia 11-06-2010 o 21:10:35 Vladimir Vassilevsky <nospam(a)nowhere.com>
napisa³(a):

>
>
> Luna Moon wrote:
>
>> Hi all,
>> I have signals that are very chaotic and choppy. I suspect that there
>> are quite a bunch of major and minor cycles inside. What's the best
>> way to detect and single out those cycles?
>> Any Matlab code around?
>> Thanks a lot!
>
> Wow, what a cretin!

Yes, loonatic moonthinking humanoid thing.
You were very precise, thank you.
Is there any cretin filtering tool?

--
Mikolaj
From: fatalist on 16 Jun 2010 09:04
On Jun 11, 2:13 pm, Luna Moon <lunamoonm...(a)gmail.com> wrote:
> Hi all,
>
> I have signals that are very chaotic and choppy. I suspect that there
> are quite a bunch of major and minor cycles inside. What's the best
> way to detect and single out those cycles?
>
> Any Matlab code around?
>
> Thanks a lot!

Forget about FFT (and the rest of regular folks in this group,
especially VLV)

Recurrence analysis is usually the best for chaotic signals

http://en.wikipedia.org/wiki/Recurrence_plot

I believe you can find plenty of matlab code if you google

From: Vladimir Vassilevsky on 16 Jun 2010 14:44


Mikolaj wrote:

> Dnia 11-06-2010 o 21:10:35 Vladimir Vassilevsky <nospam(a)nowhere.com>
> napisa³(a):
>
>>
>>
>> Luna Moon wrote:
>>
>>> Hi all,
>>> I have signals that are very chaotic and choppy. I suspect that there
>>> are quite a bunch of major and minor cycles inside. What's the best
>>> way to detect and single out those cycles?
>>> Any Matlab code around?
>>> Thanks a lot!
>>
>>
>> Wow, what a cretin!
>
>
> Yes, loonatic moonthinking humanoid thing.
> You were very precise, thank you.
> Is there any cretin filtering tool?

Cretin = gmail & (no real name) & matlab

VLV

First  |  Prev  |  Next  |  Last
Pages: 1 2 3
Prev: how do you detect spikes?
Next: Download new programs and english courses