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MathGroup Archive 2012

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Removing Outliers from List

  • To: mathgroup at smc.vnet.net
  • Subject: [mg127665] Removing Outliers from List
  • From: Murta <rodrigomurtax at gmail.com>
  • Date: Tue, 14 Aug 2012 04:20:41 -0400 (EDT)
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Hi All

    Some simple idea on how to remove the outliers from a list like this?:

    l={24, 24, 3, 2, 1, 1, 1, 1}

    to get this:
    
    l={3, 2, 1, 1, 1, 1}

I have one complicated one that need a lower sigma parameter to work:
------------------------------------------------
l={24, 24, 3, 2, 1, 1, 1, 1}

removeNormalOutliers[data_,\[Alpha]_:2.09]:=Block[{removeSub},

	removeSub[dataSub_]:=Module[{\[Sigma],\[Mu],return},
                If[Length[dataSub]>1,\[Mu]=N@Mean[dataSub];
		\[Sigma]=N@StandardDeviation[dataSub];
		return=Select[dataSub,#<=\[Mu]+\[Alpha] \[Sigma]&],dataSub]
	];
	FixedPoint[removeSub,data,20]
]

removeNormalOutliers[l, 1]
------------------------------------------------

Some better/simple idea?
tks in advance
Murta



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