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MathGroup Archive 1999

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Re: Help with Percentile formula !!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19398] Re: [mg19371] Help with Percentile formula !!
  • From: BobHanlon at aol.com
  • Date: Mon, 23 Aug 1999 13:57:13 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Mike,

Needs["Statistics`DescriptiveStatistics`"]

data = Table[500*Random[], {1000}];

?Quantile

Quantile[list, q] gives the q-th quantile of the entries in
   list (the fraction of entries in list that are less than
   this value is q).

Finding the values that correspond to 10%, 20%, ..., 100%, of the data

percentiles = Table[Quantile[data, pct/100], {pct, 10, 100, 10}]

{49.23368229765424, 110.28038943739725, 160.5545908527711, 
 206.07001160045024, 252.1836741925545, 303.5777054159099, 
 349.25003576787134, 404.0345392807842, 449.5247014457069, 
 499.9606579813818}

Checking by counting the values

Table[Length[Select[data, # <= percentiles[[pct/10]] &]], {pct, 10, 100, 10}]

{100, 200, 300, 400, 500, 600, 700, 800, 900, 1000}


Bob Hanlon

In a message dated 8/21/99 5:14:57 AM, mike_brydon at msn.com writes:

>Does anyone know the formula to work out percentiles given a list of values.


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