If the order of the sites in your table is random in itself, you can use
this approach:
select * from mytable where rowid mod 10=0
This will select record 10, 20, 30 etc.
If you want to get a better spatially spread, start by ordering the sites
according to centroidx() and centroidy().
The random function in mapbasic isn't of such great quality, which can be
seen here: www.routeware.dk/mapbasic_rnd.png
A better one, called from a DLL: www.routeware.dk/delphi_rnd.png
The source code for this can be found here:
www.routeware.dk/download/randompoints.zip
Regards
Uffe
----- Original Message -----
From: "John Nott" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, October 26, 2005 11:37 AM
Subject: MI-L Selecting a Random Sample from a Table
Hello List,
I have a table of about 5,000 sites. What I would like to do is select a
spatially random distribution of about say10% or so of these. Does
anyone know a way of doing this in MI. I suppose I could add a row ID
and do a random number generation is Excel but it would be useful for
future reference.
Thanks for any help you can offer!!
All the best,
- John
John Nott
Consultant/GIS Analyst
ROGER TYM & PARTNERS
Fairfax House, 15 Fulwood Place, London, WC1V 6HU
t 020 7831 2711
f 020 7831 7653
e [EMAIL PROTECTED]
w www.tymconsult.com
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