Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
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@xxxxxxxx] 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. 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@xxxxxxxxxxxxxxxx > For list information or to unsubscribe, visit: > http://www.unidata.ucar.edu/mailing_lists/ -- Gerry Creager -- gerry.creager@xxxxxxxx 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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