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

[Roy Mendelssohn]

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
>> _______________________________________________
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>> 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."
>
>
>
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**********************
"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."