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Generating random number within a specific range (0.5-1.5)

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Top Forums Shell Programming and Scripting Generating random number within a specific range (0.5-1.5)
# 8  
Old 04-03-2009
As pludi mentioned in the second post on this thread - you have to do it yourself.
As an alternative (which might be 'good enough' - but I doubt it with 1ms frequency), use the Search function of these forums to see other threads addressing 'randomness'.

All in all, a 1ms frequency I'd say is a bit too much for the scripting paradigm.
# 9  
Old 04-03-2009
Quote:
My script will be using the random command sometimes a few times within one second and having the same result each time is not an option..
How come you didn't say that in your first post? Nobody here can read your mind. If you want unique random numbers then that is a different situation that just random numbers. And since the amount of numbers between .5 and 1.5 is very limited you should say how many random numbers you want, otherwise all you have to do is shuffle the list of numbers in a random way and not create a list of random numbers.

Edit: never mind, I didn't read your last post that showed your usage requirements. Shuffling a list of numbers will not work for your requirements.
Last edited by KevinADC; 04-03-2009 at 02:56 PM..
# 10  
Old 04-04-2009
Hi.

Here is one method:
Code:
#!/usr/bin/env bash

# @(#) s1       Demonstrate obtaining vector of truly random values.

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) awk qrandom
set -o nounset

echo
echo " Results, 0-1:"
qrandom 10

echo
echo " Results, 0.5 - 1.5:"
qrandom 10 |
awk '
{ t = $0 + 0.5 ; printf("%.2f\n",t) }
'

exit 0

Producing a sequence (0,1) and (.5,1.5):
Code:
% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.11-x1, i686
Distribution        : Xandros Desktop 3.0.3 Business
GNU bash 2.05b.0
GNU Awk 3.1.4
qrandom (local) 1.0

 Results, 0-1:
0.4673012
0.7736701
0.9535608
0.1947628
0.8967344
0.4138898
0.9485450
0.6075562
0.9707173
0.2477338

 Results, 0.5 - 1.5:
1.27
0.57
1.00
1.01
1.26
1.47
0.63
0.84
0.92
0.91

The random number vector is obtained from an Internet service:
Quote:
We use 'Quantum Random Bit Generator' (QRBG121), which is a fast non-deterministic random bit (number) generator whose randomness relies on intrinsic randomness of the quantum physical process of photonic emission in semiconductors and subsequent detection by photoelectric effect.

More at: Quantum Random Bit Generator Service
Best wishes ... cheers, drl
# 11  
Old 04-05-2009
Quote:
Originally Posted by vgersh99
All ksh arithmetic is integer.

ksh93 does floating point arithmetic:

Code:
$ for n in 1 2 3 4 5 
> do
>  echo $(( ($RANDOM % 11 + 5) / 10. ))
> done
0.6
0.5
1.2
1.1
1.4
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