[ncl-talk] What is the method used in "dim_spi_n" function to estimate three gamma parameters of the Pearson type III distribution

[Kritanai Torsri]

Hi Mary,

Thanks for your reply.

BRG,

Kritanai



On 25-Apr-16 10:49 PM, Mary Haley wrote:
> Kritanai,
>
> Yes, by default, this function will calculate the SPI by applying a 
> 2-parameter gamma distribution fit, regardless of whether you have NCL 
> Version 6.2.1 or 6.3.0.
>
> To get the Pearson type III distribution, you need to have NCL V6.3.0 
> or later, and you need to set:
>
>   opt = True
> opt at spi_type = 3
>
> You can see full information on the dim_spi_n page:
>
> http://www.ncl.ucar.edu/Document/Functions/Built-in/dim_spi_n.shtml
>
> --Mary
>
>
> On Sun, Apr 24, 2016 at 4:44 AM, Kritanai Torsri <kritanai at haii.or.th 
> <mailto:kritanai at haii.or.th>> wrote:
>
>     Dear All,
>
>     I used the "dim_spi_n" function with the Pearson type III to
>     compute SPI.
>
>     Am I correct that, by default, the NCL function still used the Maximum
>     likelihood to estimate
>
>     the location, scale, and shape of the gamma distribution as in
>     two-parameter gamma distribution or it uses another method?
>
>     If any one know, please give me suggestion and thanks in advance.
>
>     BRGs,
>
>     Kritanai Torsri
>
>     Assistant Researcher
>
>     Hydro and Agro Infomatics Institute, Bangkok, Thailand.
>
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