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BlueEdger

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Determining Most Common Value in an Array

Hello,

Is there anyway I can determine the most common value in an array?

Say my array contains 1,1,2,2,2,2,3

How do I get that 2 is the most common value??

Is this at all possible?

Thanks for your help.
Avatar of avner
avner
Here is an example of something like that :

<html>
<head>
<title>about:blank</title>
<script language="javascript1.2">
<!-- copyright(c) avcoh@yahoo.com
function calculateWords(sName)
{
var oField = document.getElementById(sName);
var sString = oField.innerText;
sString =sString.replace(","," ");
sString =sString.replace(/\n|\r/g," ");
sString =sString.replace("  "," ");
var arr = new Object();
var arrWords = sString.split(" ");
for (var i=0;i<arrWords.length;i++)
      {
      var sWord = arrWords[i];

            if (arr[sWord])
            {
                  arr[sWord]=arr[sWord]+1;
            }
            else
            {
                  arr[sWord] = 1
            }
      }

var s = "Total of words in textarea :\n";
for (var i in arr)
      {
            s+="["+i+"] count is :" + arr[i] + "\n";
      }

alert(s);

}
-->
</script>
<style>

</style>
</head>
<body  onload="calculateWords('ta')"
<textarea id="ta" cols="40" rows="30">
this is a list of this is ah words
this is a list of this is ah words
this is a list of this is ah words
this is a list of this is ah words
this is a list of this is ah words
this is a list of this is ah words
this is a list of this is ah words
this is a list of this is ah words</textarea>
</body>
</html>
Avatar of Zvonko
Zvonko
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Like this:

<script>

var myArray = ["Atext","Atext","Btext","Btext","Btext","Btext","Ctext"];

alert(mC(myArray));


function mC(theArray){
  tempArray = theArray.slice(0,theArray.length);
  tempArray.sort()
  mVal = aVal = "";
  mCnt = aCnt = 0;
  for(i=0;i<tempArray.length;i++){
    if(aVal!=theArray[i]){
      if(aCnt>mCnt){
        mCnt = aCnt;
        mVal = aVal
      }
      aVal = theArray[i];
      aCnt = 1;
    } else {
      aCnt++;
    }
  }
  return [mVal, mCnt];
}
</script>

Avatar of Zvonko
Zvonko
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The text values are only for better visulisation.
Of course does the mC() function work also for digits:

<script>

var myArray = [1,1,2,2,2,2,3];

alert(mC(myArray));


function mC(theArray){
  tempArray = theArray.slice(0,theArray.length);
  tempArray.sort()
  mVal = aVal = "";
  mCnt = aCnt = 0;
  for(i=0;i<tempArray.length;i++){
    if(aVal!=theArray[i]){
      if(aCnt>mCnt){
        mCnt = aCnt;
        mVal = aVal
      }
      aVal = theArray[i];
      aCnt = 1;
    } else {
      aCnt++;
    }
  }
  return [mVal, mCnt];
}
</script>

Avatar of avner
avner
Zvonko, your code is incorrect :


Try to have this array :
var myArray = ["Atext","Atext","Btext","Btext","Btext","Btext","Ctext", "Atext", "Atext", "Atext"];
Avatar of BlueEdger
BlueEdger

ASKER

Zvonko,

My array contains 0.445,0.445,0.783,0.783,0.783,0.881

Your mC function is returning ,0

If I step through the tempArray I get the individual values but the last one is this ,0

aVal returns the correct 0.783, but then also ,0

I cant work out why it is doing that??
Avatar of Zvonko
Zvonko
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Thanks, it was a typo. I did not use the sorted tempArray.

Here the correction:

<script>

var myArray = ["Atext","Atext","Btext","Btext","Btext","Btext","Ctext", "Atext", "Atext", "Atext"];

alert(mC(myArray));


function mC(theArray){
  tempArray = theArray.slice(0,theArray.length);
  tempArray.sort()
  mVal = aVal = "";
  mCnt = aCnt = 0;
  for(i=0;i<tempArray.length;i++){
    if(aVal!=tempArray[i]){
      if(aCnt>mCnt){
        mCnt = aCnt;
        mVal = aVal
      }
      aVal = tempArray[i];
      aCnt = 1;
    } else {
      aCnt++;
    }
  }
  return [mVal, mCnt];
}
</script>

Avatar of Zvonko
Zvonko
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BlueEdger, try please again. Now it works: 0.783, 3 times.
Avatar of BlueEdger
BlueEdger

ASKER

I've tried it with one array where the last four values are all the same, and I get the right result.  But when I tried it where all the values where the same except for the last one, then I get last value,1.

Can you test your function with this criteria and see if you get the same thing??
ASKER CERTIFIED SOLUTION
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Zvonko
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Avatar of Zvonko
Zvonko
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This version works now even with one single array element.
Avatar of BlueEdger
BlueEdger

ASKER

Thanks Zvonko, that works a treat.  Avner, Im sorry I did not test your solution as Zvonko's function was neater, and hence I am awarding Zvonko the points as that was the solution I used.  
Avatar of Zvonko
Zvonko
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Thanks for the points and for your feedback.

@avner: thank you for helping me finding errors.
Here are your points: http:Q_20871628.html
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Zvonko
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Uhps, sorry I though this was a five hundred pointer!
Anyway, take it :)
Avatar of a_twixt_in_the_tale
a_twixt_in_the_tale
just 4 fun
<script language="javascript">
      var myArray = ["Atext","Btext","Btext","Btext","Btext","Btext","Ctext", "Atext", "Atext","Ctext"];
      var c = new Array();
      for (var i=0; i<myArray.length; i++)
            c[""+myArray[i]]=isNaN(c[""+myArray[i]])?0:c[""+myArray[i]]+1;
      var mi=""+myArray[0];
      for (i in c)
            if (c[mi]<c[i])
                  mi=i;
      alert(mi);
</script>

:)
Don
Avatar of Zvonko
Zvonko
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Nice idea, the same as from avner: using associative arrays.
But with same beginning errors like mine: you did not test it :)
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Zvonko
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Sorry twixt, I did test it wrong. Your method works correct.