Aykırı Gözlemlerin Varlığında Uyarlanmış En Küçük Kovaryans Determinant Tahminine Dayalı Dayanıklı Temel Bileşenler Analizi

Year 2016, , 85 - 94, 08.12.2016

B. Barış Alkan

https://doi.org/10.17093/aj.2016.4.2.5000189525

Cited By: 2

Abstract

Klasik temel bileşenler analizi (KTBA), çok değişkenli veri kümelerinde yer alabilen aykırı gözlemlere karşı dayanıklı değildir. Aykırı gözlemlerin varlığında KTBA kullanılarak elde edilen sonuçlar gerçekte olması gerekenden oldukça farklı çıkabilir. Bu yüzden, aykırı gözlemlerin varlığında PCA’nın dayanıklı versiyonlarının kullanımı tercih edilmelidir. Dayanıklı temel bileşenler elde etmek için en kolay yol konum ve ölçek parametrelerinin klasik tahminleriyle, onların dayanıklı tahminlerinin yer değiştirilmesidir. Çok değişkenli veri kümesi için konum ve ölçek parametrelerinin dayanıklı tahmini, yüksek bozulma noktası sağlayan en küçük kovaryans determinant (EKKD) yöntemi ile yapılabilir. Bu çalışmada, EKKD yöntemi, jacknife yeniden örnekleme yaklaşımı kullanılarak uyarlanıp, bu uyarlamadan kaynaklanan değişimlerin dayanıklı temel bileşenler analizi (DTBA) üzerindeki etkileri incelenmesi amaçlanmaktadır. Jackknife yeniden örnekleme yöntemine dayanan EKKD’nin aykırı gözlem oranındaki değişmelerden nasıl etkilendiği iki gerçek veri kümesi üzerinden değerlendirilmektedir. Elde edilen bulgular ışığında, önerilen uyarlanmış en küçük kovaryans determinant (UEKKD) tahminine dayalı DTBA, klasik EKKD’ye dayanan DTBA’ya göre veri kümesinde aykırı gözlemlerin varlığında daha iyi sonuçlar verdiği görülmektedir. 

Robust Principal Component Analysis Based On Modified Minimum Covariance Determinant In The Presence Of Outliers

Abstract

Principal component analysis (PCA) is not resistant to outliers existing in multivariate data sets. The results which are obtained by using classical PCA are far from real values in the presence of outliers. Therefore, using robust versions of PCA is favorable. The easiest way to obtain robust principal components is to replace classical estimates of the location and scale parameters with their robust versions. Robust estimations of location and scale parameters can be found with minimum covariance determinant (MCD) providing high breakdown point. In this study, algorithm of MCD is modified using Jackknife resampling approach and results of this modification are examined. Proposed  robust principal component analysis (RPCA) based on modified MCD (MMCD) method that is modified using Jaccknife resampling are evaluated over two real data with different outlier ratios. In the light of obtained results, it can be said that RPCA based on MMCD is better than RPCA based on MCD in the presence of outliers.

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