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Entropy: Difference between revisions
→Euler Math Toolbox: Added Excel solution
imported>Arakov |
imported>Meadpusher (→Euler Math Toolbox: Added Excel solution) |
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Line 1,008:
>entropy("1223334444")
1.84643934467</syntaxhighlight>
=={{header|Excel}}==
This solution uses the <code>LAMBDA</code>, <code>LET</code>, and <code>MAP</code> functions introduced into the Microsoft 365 version of Excel in 2021. The <code>LET</code> function is able to use functions as first class citizens. Taking advantage of this makes the solution much simpler. The solution below looks for the string in cell <code>A1</code>.
<syntaxhighlight lang="excel">
=LET(
_MainS,A1,
_N,LEN(_MainS),
_Chars,UNIQUE(MID(_MainS,SEQUENCE(LEN(_MainS),1,1,1),1)),
calcH,LAMBDA(_c,(_c/_N)*LOG(_c/_N,2)),
getCount,LAMBDA(_i,LEN(_MainS)-LEN(SUBSTITUTE(_MainS,_i,""))),
_CharMap,MAP(_Chars,LAMBDA(a, calcH(getCount(a)))),
-SUM(_CharMap)
)
</syntaxhighlight>
_Chars uses the <code>SEQUENCE</code> function to split the text into an array. The <code>UNIQUE</code> function then returns a list of unique characters in the string.
<code>calcH</code> applies the calculation described at the top of the page that will then be summed for each character
<code>getCount</code> uses the <code>SUBSTITUTE</code> method to count the occurrences of a character within the string.
If you needed to re-use this calculation then you could wrap it in a <code>LAMBDA</code> function within the name manager, changing <code>A1</code> to a variable name (e.g. <code>String</code>):
<syntaxhighlight lang="excel">
ShannonEntropyH2=LAMBDA(String,LET(_MainS,String,_N,LEN(_MainS),_Chars,UNIQUE(MID(_MainS,SEQUENCE(LEN(_MainS),1,1,1),1)),calcH,LAMBDA(_c,(_c/_N)*LOG(_c/_N,2)),getCount,LAMBDA(_i,LEN(_MainS)-LEN(SUBSTITUTE(_MainS,_i,""))),_CharMap,MAP(_Chars,LAMBDA(a, calcH(getCount(a)))),-SUM(_CharMap)))
</syntaxhighlight>
Then you can just use the named lambda. E.g. If A1 = 1223334444 then:
<syntaxhighlight lang="excel">
=ShannonEntropyH2(A1)
</syntaxhighlight>
Returns 1.846439345
=={{header|F_Sharp|F#}}==
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