| What is 'iadj' and 'iend' in TRIANGULATION? [message #62751] |
Wed, 01 October 2008 07:14  |
Karlo Janos
Messages: 31
Registered: July 2008
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Hello all!
I'd like to use IDL's function TRIANGULATION for determining the
nearest neighbor on the surface of a sphere. Unfortunately the keyword
'CONNECTIVITY' doesn't work together with 'SPHERE'. But I found in the
struct of SPHERE the fields 'iadj' and 'iend'. What do they mean? I did
not find any explanation about this struct.
Best regards
Karlo
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| Re: What is 'iadj' and 'iend' in TRIANGULATION? [message #62805 is a reply to message #62751] |
Sat, 04 October 2008 04:16  |
Karlo Janos
Messages: 31
Registered: July 2008
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Member |
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> The output of the SPHERE keyword is designed to be passed to the
> TRIGRID function. The TRIANGULATE helpfile states that 'The structure
> contains the 3D Cartesian locations sample points
Indeed, that's easy to understand, because the field is called ".XYZ".
> and the adjacency
> list that describes the triangulation.', so I'm guessing .iadj
> and .iend are fields that contain information about the adjacency
> list.
> If you want to find out what the arrays in these structure fields
> actually _mean_, then I'm afraid I'm no use to you! :-/
That is the point. I want to know how to interpret the numbers in these
structure fields .IADJ (sounds like adjacency) and .IEND (no idea what
that means). But it does not seem to be the same principle as if I would
use the CONNECTIVITY keyword to get the adjacency list in planar
gridding (there is nothing like .IEND).
Thanks for your guess!
Karlo
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| Re: What is 'iadj' and 'iend' in TRIANGULATION? [message #62817 is a reply to message #62751] |
Fri, 03 October 2008 06:33 |
Spon
Messages: 178
Registered: September 2007
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Senior Member |
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On Oct 1, 3:14 pm, "Karlo Janos" <idl.20.beam...@spamgourmet.com>
wrote:
> Hello all!
>
> I'd like to use IDL's function TRIANGULATION for determining the
> nearest neighbor on the surface of a sphere. Unfortunately the keyword
> 'CONNECTIVITY' doesn't work together with 'SPHERE'. But I found in the
> struct of SPHERE the fields 'iadj' and 'iend'. What do they mean? I did
> not find any explanation about this struct.
> Best regards
>
> Karlo
Hi Karlo,
The output of the SPHERE keyword is designed to be passed to the
TRIGRID function. The TRIANGULATE helpfile states that 'The structure
contains the 3D Cartesian locations sample points and the adjacency
list that describes the triangulation.', so I'm guessing .iadj
and .iend are fields that contain information about the adjacency
list. Have a look at Example 2 in the TRIGRID helpfile.
If you want to find out what the arrays in these structure fields
actually _mean_, then I'm afraid I'm no use to you! :-/
Regards,
Chris
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