# CFLib.org – Common Function Library Project

## Percentile(number, aPopulation[, insertNumber])

##### Last updated July 30, 2001

Version: 1 | Requires: CF5 | Library: MathLib

Description:
This function is used to get the percentile rank of a given number from a population of numbers. The percentile refers to the percent of numbers in the set that are below the number you pass in.

Return Values:
Returns a numeric percent value

Example:

``````<cfset population="33,29,29,31,32,33,33,35,37,25,28">
<cfset array = listToArray(population)>
<table>
<tr>
<td>Number to Check</td>
<td>Percentile</td>
</tr>
<cfoutput>
<cfloop from="1" to="#arraylen(array)#" index="ii">
<cfset thisNumber = array[ii]>
<tr>
<td>#thisNumber#</td>
<td>#percentile(thisNumber,array)#</td>
</tr>
</cfloop>
</cfoutput>
</table>
``````

Parameters:

Name Description Required
number The number you want to get the percentile rank of Yes
aPopulation An array of numbers which is the population to find the percentile in Yes
insertNumber Boolean value to decide if the number should be inserted into the population before calculation. By default this is false. No

Full UDF Source:

``````/**
* Function for calculating the percentile of a given number from a population of numbers.
*
* @param number      The number you want to get the percentile rank of
* @param aPopulation      An array of numbers which is the population to find the percentile in
* @param insertNumber      Boolean value to decide if the number should be inserted into the population before calculation.  By default this is false.
* @return Returns a numeric percent value
* @author Nathan Dintenfass (nathan@changemedia.com)
* @version 1, July 30, 2001
*/
function percentile(numberToCheck,populationArray){
// (Thanks to Jim Flannery for pointing me at the formula).
var ii = 1;
//set a counter for the number below this value
var countBelow = 0;
//set a counter for how many instances of thisNumber there are
var countWithin = 0;
// deal with the optional parameter as to whether the number to check is to be added to the population.
//if there a third argument and it is a boolean and it is true, insert the number to check
if(arraylen(arguments) gt 2 AND isBoolean(arguments) and arguments)
arrayAppend(populationArray,numberToCheck);
//now, let's sort the array to make it easier to find the values
arraySort(populationArray,"numeric");
//loop through the array, setting the counters appropriately
for(ii = 1; ii lte arraylen(populationArray); ii = ii + 1){
//if this number is below numberToCheck, increment the countBelow
if(populationArray[ii] lt numberToCheck){
countBelow = countBelow + 1;
}
else{
//if this number is equal to numberToCheck, increment the counterWithin
if(populationArray[ii] eq numberToCheck){
countWithin = countWithin + 1;
}
//if this number is above the numberToCheck break
else{
break;
}
}
}
//run the percentile formula and return
return ((countBelow + 0.5 * countWithin)/arraylen(populationArray))*100;
}
``````

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