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MathGroup Archive 2006

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Re: sparsearray and random

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71456] Re: sparsearray and random
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Sun, 19 Nov 2006 01:10:11 -0500 (EST)

On 11/18/06 at 4:41 AM, Arkadiusz.Majka at gmail.com wrote:

>a = Random[Integer, {3, 7}]
>Normal[SparseArray[(i_ /; 3 â?¤ i â?¤ a) -> p, 10]]

>is not the same as this:

>Normal[SparseArray[(i_ /; 3 â?¤ i â?¤Random[Integer, {3, 7}] ) -> p,
>10]]

In the first case you generate a single random number. In the 
second case you generate a random number for each position for 
each element of the array.

Compare

a = Random[Integer, {3, 7}]
SparseArray[i_ /; 3 <= i <= a -> p, 10]//Trace

to

SparseArray[i_ /; 3 <= i <= Random[Integer, {3, 7}] -> p,
   10]//Trace
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