TideMan <mulgor@gmail.com> wrote in message <3ce8f93600e44d46932e0aba08c03375@b34g2000prf.googlegroups.com>...
> On Sep 5, 12:44 am, "edward kabanyas" <djuky_...@yahoo.com> wrote:
> > Hi all,
> >
> > I would like to ask your share about the recurrence frequency analysis in Matlab. As far as I know, the recurrence frequency is the time interval of an event will be repeated again in the coming time such as used in flooding or earthquake prediction.
> >
> > For example (only example but real data also hourly), I have hourly rainfall data in mm during one years observation. I want to calculate the recurrence frequency of one per day, one per two days, one per weeks, one per months. The number of sample is 10,000 in minute interval.
> >
> > To calculate the recurrence, assumed 1 years data (365 days), we sort data (10,000 samples) from a large to a small and take the 365th data, don't we ? Or another way ?
> >
> > For one per months, we sort the data from a large to a small and the 12th data, or another correct way ?
> >
> > Thanks for sharing..
> >
> > Edward
>
> No.
> You first must reshape the data into blocks of 1 day, 1 month, 1 year,
> or whatever, then take the maximum of each block and sort the maxima.
> Then, you need a mapping formula for the probabilty.
> Here is Gringorten's for annual flood data:
> p_i=(ia)/(n+0.12)
> where p_i is the Annual Exceedance Probability (inverse of recurrence
> interval) for the ith position, a is a constant, usually 0.44, and n
> is the number of data. An AEP of 0.01 is the 100year flood.
> You plot your sorted maxima as a function of p_i.
Hi TideMan,
thanks for reply. I want to calculate the recurrence of cloud with certain size, is it acceptable to use Gringorten equation for mapping formula for the probabilty ? What I understand, to get the value of certain recurrence frequencies we can use interpolation procedure of the plot, can we ?
Thanks for help
Edward
