[mirtoolbox] Re: Problems with MIRPEAKS and other...
- From: Luca Piccina <luca.piccina@xxxxxxxxx>
- To: mirtoolbox@xxxxxxxxxxxxx
- Date: Sat, 14 Mar 2009 20:33:23 +0100
Hello Olivier,
thanks a lot for the reply. It's all quite clear (even if some
mathematics references will be appreciated :) )
I have a doubt about PeriodFreq and PeriodAmp anyway:
if the periodicity is estimated peak picking for the maximum of the
(excluding lag 0, i Imagine) autocorrelation function, to output NaN
means that there is NO peak at all or that peak below a certain
threshold are discarded?
Thanks as always
Luca
2009/3/14 Olivier Lartillot <olivier.lartillot@xxxxxxxxxxxxx>:
> Hi Luca and others,
> I just extended the documentation of mirstat, as follows:
>
> If the object is frame-decomposed, the fields of the output are:
>
> Mean: the average along frames;
> Std: the standard deviation along frames;
> Slope: the linear slope of the trend along frames, i.e. the derivative of
> the line that would best fit the curve. The slope S is computed in a
> normalised representation of the curve C – i.e., centered, with unit
> variance, and with a temporal scale reduced to a series T of values between
> 0 and 1 – as a solution in a least-square sense of the equation S*T = C;
> PeriodFreq: the frequency (in Hz.) of the maximal periodicity detected in
> the frame-by-frame evolution of the values, estimated through the
> computation of the autocorrelation sequence. If no periodicity is detected,
> NaN is returned;
> PeriodAmp: the normalized amplitude of that main periodicity, i.e., such
> that the autocorrelation at zero lag is identically 1.0. The first
> descending slope starting from zero lag is removed from this analysis, as it
> is not related to the periodicity of the curve.
> PeriodEntropy: the Shannon entropy of the autocorrelation function (cf.
> mirentropy).
>
> Is it clear? Does anyone know any references related to these concepts?
> Olivier
> Luca Piccina kirjoitti 11.3.2009 kello 14.21:
>
> Hello,
> I am Luca from Italy and I would need some theorical references for
> the statistics implemented with mirstat. It's ok with the mean and the
> variance, but I'd like a better understanding of Slope, PeriodFreq,
> PeriodAmp and PeriodFreq...could you please give me some references?
> Thanks in advance, best wishes
>
> Luca
>
>
>
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