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Re: Random selection of pairs [message #51252 is a reply to message #51246]

Sat, 11 November 2006 06:58

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article <1163249745.126148.50070@h48g2000cwc.googlegroups.com>,
"Julio" <julio@cpa.unicamp.br> wrote:

> I have an array with two columns and a thousand of rows. Each row has a
> pair of latitude and longitude.
>
> Array=float(2, 1000)
>
> -27.3456 -54.6529
> -23.4546 -56.7263
> ... and so on...
>
> I need to retrieve only 100 pairs, randomly. How can I do that?
> Any comments welcome!
> Julio

It will be much simpler, and probably much quicker, to read all
of the pairs and then pick 100 randomly, like this script named
select_random:

x = findgen(2, 1000) ;create fake lon-lat data
r = RANDOMU(seed, 1000) ;generate random numbers
j = (SORT(r))[0:9] ;find indices of 10 smallest numbers
PRINT, j
PRINT, r[j]
FOR k = 0, 9 DO PRINT, x[*,j[k]] ;print 10 random pairs

IDL> @select_random
952 848 497 935 490 678 853 313
365 976
0.000964510 0.00113783 0.00255171 0.00340872 0.00390364 0.00452789 0.00609691
0.00676597 0.0117514 0.0121868
1904.00 1905.00
1696.00 1697.00
994.000 995.000
1870.00 1871.00
980.000 981.000
1356.00 1357.00
1706.00 1707.00
626.000 627.000
730.000 731.000
1952.00 1953.00

Ken Bowman

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[Message index]

		Re: Random selection of pairs By: Julio[1] on Sun, 12 November 2006 04:55
		Re: Random selection of pairs By: Michael Galloy on Sat, 11 November 2006 20:30
		Re: Random selection of pairs By: Kenneth P. Bowman on Sat, 11 November 2006 06:58

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