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

[Roy Mendelssohn]

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
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>
> -- 
> 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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Roy Mendelssohn
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NOAA/NMFS
Environmental Research Division	
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