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Entropy: Difference between revisions
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The '''LOG2''' subroutine is only included here for functionality, not to document how to calculate LOG<sub>2</sub> using REXX.
<lang rexx>/*REXX program calculates the information entropy for a
numeric digits length( e() ) % 2 - length(.) /*use 1/2 of the decimal digits of E. */
parse arg $; if $='' then $= 1223334444 /*obtain the optional input from the CL*/
#=0
$$= /*initialize the $$ list. */
do j=1 for L; _= substr($, j, 1) /*process each character in $ string.*/
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say ' input string: ' $
say 'string length: ' L
say ' unique chars: ' #
say 'the information entropy of the string ──► ' format(sum,,12) " bits."
exit /*stick a fork in it, we're all done. */
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ox=izz; ii=ii+is*2**j; end /*while*/; x= x * e** -ii -1; z= 0; _= -1; p= z
do k=1; _= -_ * x; z= z+_/k; if z=p then leave; p= z; end /*k*/
r= z + ii; if arg()==2 then return r; return r / log2(2, .)</lang>
{{out|output|text= when using the default input of: <tt> 1223334444 </tt>}}
<pre>
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