20050603: Use of Java udunits package

Peter,

> To: support@xxxxxxxxxxxxxxxx
> From: Peter Hollemans <Peter.Hollemans@xxxxxxxx>
> Subject: Use of Java udunits package.
> Organization: NOAA
> Keywords: 200506031601.j53G1GZu004496 netCDF-Java UDUNITS

The above message contained the following:

> I recently became aware of the udunits Java port from this support message:
> 
> http://my.unidata.ucar.edu/content/support/help/MailArchives/netcdf-java/msg00148.html
> 
> I downloaded the source code file ncSrc-2.2.zip and created Javadocs for 
> the ucar.units package so I could read the API as it's not in the 
> standard online Javadocs (I guess because people are supposed to use the 
> ucar.nc2.units package).
> 
> My question is this.  The C language version of udunits contains the 
> utConvert() function, which returns the y=ax+b coefficients for a units 
> conversion.  Is there an equivalent method in the Java API, or some way 
> to recover those coefficients?  There are some ways that I can think of 
> to get them, such as using the Unit.convertTo(double,Unit) and passing 
> in zero to get the additive constant b, and then 1 to get the 
> multiplicative constant a as y-b.  But I thought there must be some 
> better way supported by a Java API method.

One of the goals of an object-oriented programming language like Java is
to insulate the user of a class from the implementation of the class.
The fact that a convertion between units might be Gaussian (y = ax + b)
or linear (y = ax) or logarithmic (y = A lg(x)) is hidden from the user
of the classs.  Doing what you want would make the implementation
visible and cast the implementation in concrete -- preventing better or
different implementations.

Why would you want the coefficients?

> Peter.
> 
> --------------000908080704010705090505
> Content-Type: text/x-vcard; charset=utf-8;
>  name="Peter.Hollemans.vcf"
> Content-Transfer-Encoding: 7bit
> Content-Disposition: attachment;
>  filename="Peter.Hollemans.vcf"
> 
> begin:vcard
> fn:Peter Hollemans
> n:Hollemans;Peter
> email;internet:Peter.Hollemans@xxxxxxxx
> title:SP Systems, Inc. Consultant for NOAA/NESDIS
> tel;work:(250) 478-1006
> version:2.1
> end:vcard
> 
> 
> --------------000908080704010705090505--

Regards,
Steve Emmerson

> NOTE: All email exchanges with Unidata User Support are recorded in the
> Unidata inquiry tracking system and then made publicly available
> through the web.  If you do not want to have your interactions made
> available in this way, you must let us know in each email you send to us.


  • 2005 messages navigation, sorted by:
    1. Thread
    2. Subject
    3. Author
    4. Date
    5. ↑ Table Of Contents
  • Search the netcdf-java archives: