[netcdfgroup] Calculating medians, quartiles etc of a variable in a NetCDF file. [SEC=UNCLASSIFIED]

[Henry Butowsky]

Hi Tim,
    Im a netcdf programmer -It may be possible to write a custom 
operator for nco tool "ncap2" that calculates quartiles
    Regards Henry


Roy Mendelssohn wrote:
> R has functions for trimmed means also,
>
> -Roy M.
>
> On May 11, 2008, at 8:09 PM, Roy Mendelssohn wrote:
>
>   
>> R.  And it has netcdf functions also.
>>
>> -Roy M.
>>
>> On May 11, 2008, at 8:07 PM, Timothy Hume wrote:
>>
>>     
>>> I think the reason why functions for calculating quartiles (or more
>>> generally, percentiles) are not in many software packages is
>>> because they can be computationally expensive to compute.
>>>
>>> The only way I know how to generate percentiles is to first sort
>>> the data into numeric order, and then select the appropriate value
>>> from the list. Sorting is expensive, especially when there are a
>>> lot of data. Is there a better/faster way of computing percentiles?
>>>
>>> Tim Hume
>>> Centre for Australian Weather and Climate Research
>>> Melbourne
>>> Australia
>>>
>>> -----Original Message-----
>>> From: Gerry Creager [mailto:gerry.creager at tamu.edu]
>>> Sent: Monday, 12 May 2008 12:41
>>> To: Timothy Hume
>>> Cc: Dennis Shea
>>> Subject: Re: [netcdfgroup] Calculating medians, quartiles etc of a
>>> variable in a NetCDF file. [SEC=UNCLASSIFIED]
>>>
>>> I'd consider looking at the NCAR command language and seeing if
>>> quartile
>>> calculation is native therein.  I'd be surprised if it's not, or
>>> easily
>>> computable, but I did not find it initially.
>>>
>>> Check http://www.ncl.ucar.edu/ and consider joining the mailing list
>>> long enough to find out.
>>>
>>>
>>>
>>> Timothy Hume wrote:
>>>       
>>>> Hi,
>>>>
>>>> I have an application where I would like to calculate quartiles of
>>>> a variable in a NetCDF file (I am computing the trimean: TM = 0.25*
>>>> (Q1 + 2Q2 + Q3) )
>>>>
>>>> The NetCDF operators are excellent for computing arithmetic means,
>>>> but don't include the capability to compute quartiles. Before I
>>>> start writing my own code to compute quartiles, does anyone know
>>>> of some software which already does this? Basically, I am looking
>>>> for the equivalent of ncwa with a quartile operation.
>>>>
>>>> Thanks,
>>>>
>>>> Tim Hume
>>>> Centre for Australian Weather and Climate Research
>>>> Melbourne
>>>> Australia
>>>> _______________________________________________
>>>> netcdfgroup mailing list
>>>> netcdfgroup at unidata.ucar.edu
>>>> For list information or to unsubscribe,  visit: http://
>>>> www.unidata.ucar.edu/mailing_lists/
>>>>         
>>> --  
>>> Gerry Creager -- gerry.creager at tamu.edu
>>> Texas Mesonet -- AATLT, Texas A&M University	
>>> Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
>>> Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX  
>>> 77843
>>> _______________________________________________
>>> netcdfgroup mailing list
>>> netcdfgroup at unidata.ucar.edu
>>> For list information or to unsubscribe,  visit: http://
>>> www.unidata.ucar.edu/mailing_lists/
>>>       
>> **********************
>> "The contents of this message do not reflect any position of the U.S.
>> Government or NOAA."
>> **********************
>> Roy Mendelssohn
>> Supervisory Operations Research Analyst
>> NOAA/NMFS
>> Environmental Research Division	
>> Southwest Fisheries Science Center
>> 1352 Lighthouse Avenue
>> Pacific Grove, CA 93950-2097
>>
>> e-mail: Roy.Mendelssohn at noaa.gov (Note new e-mail address)
>> voice: (831)-648-9029
>> fax: (831)-648-8440
>> www: http://www.pfeg.noaa.gov/
>>
>> "Old age and treachery will overcome youth and skill."
>>
>>
>>
>> _______________________________________________
>> netcdfgroup mailing list
>> netcdfgroup at unidata.ucar.edu
>> For list information or to unsubscribe,  visit: http:// 
>> www.unidata.ucar.edu/mailing_lists/
>>     
>
> **********************
> "The contents of this message do not reflect any position of the U.S.  
> Government or NOAA."
> **********************
> Roy Mendelssohn
> Supervisory Operations Research Analyst
> NOAA/NMFS
> Environmental Research Division	
> Southwest Fisheries Science Center
> 1352 Lighthouse Avenue
> Pacific Grove, CA 93950-2097
>
> e-mail: Roy.Mendelssohn at noaa.gov (Note new e-mail address)
> voice: (831)-648-9029
> fax: (831)-648-8440
> www: http://www.pfeg.noaa.gov/
>
> "Old age and treachery will overcome youth and skill."
>
>
>
> _______________________________________________
> netcdfgroup mailing list
> netcdfgroup at unidata.ucar.edu
> For list information or to unsubscribe,  visit: http://www.unidata.ucar.edu/mailing_lists/ 
>
>
>