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Re: Duplicate lat/long points [message #64863 is a reply to message #64779]

Wed, 21 January 2009 07:14

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

On Jan 20, 8:57 am, hethomas <het...@googlemail.com> wrote:
> Thank you all for your responses - I am still trying to get the
> histogram method working, but have come up with a temporary working
> solution using UNIQ and running it over two FOR loops.
> James - my problem wasn't as complicated as yours, as all my points
> are the same precision, so that identical points are truly exactly the
> same. Thanks for sharing your method though. May be useful later! (I
> can't easily move to R as I am using IDL coupled with ENVI for
> satellite data work . . .)
>
> Helen

How about turning each (lat,lon) pair into a single unique index?
Since the latitudes are bounded by (-90,+90) the following mapping
function should work:

onedcoord = (lats+90) + 200*lons

You can then just run onedcoord through sort and uniq and just use one
for loop (or probably none if you're clever enough...).

-Jeremy.

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[Message index]

		Duplicate lat/long points By: hethomas on Wed, 14 January 2009 02:21
		Re: Duplicate lat/long points By: Jeremy Bailin on Thu, 15 January 2009 08:00
		Re: Duplicate lat/long points By: mccreigh on Fri, 16 January 2009 11:55
		Re: Duplicate lat/long points By: hethomas on Tue, 20 January 2009 05:57
		Re: Duplicate lat/long points By: Jeremy Bailin on Wed, 21 January 2009 07:14
		Re: Duplicate lat/long points By: Jeremy Bailin on Thu, 22 January 2009 06:58
		Re: Duplicate lat/long points By: mccreigh on Wed, 21 January 2009 08:02

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