nips nips2013 nips2013-283 knowledge-graph by maker-knowledge-mining
Source: pdf
Author: Fang Han, Han Liu
Abstract: In this paper we focus on the principal component regression and its application to high dimension non-Gaussian data. The major contributions are two folds. First, in low dimensions and under the Gaussian model, by borrowing the strength from recent development in minimax optimal principal component estimation, we first time sharply characterize the potential advantage of classical principal component regression over least square estimation. Secondly, we propose and analyze a new robust sparse principal component regression on high dimensional elliptically distributed data. The elliptical distribution is a semiparametric generalization of the Gaussian, including many well known distributions such as multivariate Gaussian, rank-deficient Gaussian, t, Cauchy, and logistic. It allows the random vector to be heavy tailed and have tail dependence. These extra flexibilities make it very suitable for modeling finance and biomedical imaging data. Under the elliptical model, we prove that our method can estimate the regression coefficients in the optimal parametric rate and therefore is a good alternative to the Gaussian based methods. Experiments on synthetic and real world data are conducted to illustrate the empirical usefulness of the proposed method. 1
Reference: text
sentIndex sentText sentNum sentScore
1 edu Abstract In this paper we focus on the principal component regression and its application to high dimension non-Gaussian data. [sent-3, score-0.387]
2 First, in low dimensions and under the Gaussian model, by borrowing the strength from recent development in minimax optimal principal component estimation, we first time sharply characterize the potential advantage of classical principal component regression over least square estimation. [sent-5, score-0.778]
3 Secondly, we propose and analyze a new robust sparse principal component regression on high dimensional elliptically distributed data. [sent-6, score-0.49]
4 The elliptical distribution is a semiparametric generalization of the Gaussian, including many well known distributions such as multivariate Gaussian, rank-deficient Gaussian, t, Cauchy, and logistic. [sent-7, score-0.216]
5 It allows the random vector to be heavy tailed and have tail dependence. [sent-8, score-0.115]
6 Under the elliptical model, we prove that our method can estimate the regression coefficients in the optimal parametric rate and therefore is a good alternative to the Gaussian based methods. [sent-10, score-0.261]
7 1 Introduction Principal component regression (PCR) has been widely used in statistics for years (Kendall, 1968). [sent-12, score-0.203]
8 Take the classical linear regression with random design for example. [sent-13, score-0.157]
9 The classical linear regression model and simple principal component regression model can be elaborated as follows: (Classical linear regression model) Y = Xβ + ; (Principal Component Regression Model) Y = αXu1 + , (1. [sent-18, score-0.677]
10 , xn )T ∈ Rn×d , Y ∈ Rn , ui is the i-th leading eigenvector of Σ, and ∈ Nn (0, σ 2 Id ) is independent of X, β ∈ Rd and α ∈ R. [sent-22, score-0.076]
11 The principal component regression then can be conducted in two steps: First we obtain an estimator u1 of u1 ; Secondly we project the data in the direction of u1 and solve a simple linear regression in estimating α. [sent-24, score-0.554]
12 1), it is easy to observe that the principal component regression model is a subset of the general linear regression (LR) model with the constraint that the regression coefficient β is proportional to u1 . [sent-26, score-0.607]
13 There has been a lot of discussions on the advantage of principal component regression over classical linear regression. [sent-27, score-0.434]
14 In low dimensional settings, Massy (1965) pointed out that principal component regression can be much more efficient in handling collinearity among predictors compared to the linear regression. [sent-28, score-0.434]
15 More recently, Cook (2007) and Artemiou and Li (2009) argued that principal component regression has potential to play a more important role. [sent-29, score-0.387]
16 In particular, letting uj be the j-th leading eigenvector of the sample covariance matrix Σ of x1 , . [sent-30, score-0.101]
17 This indicates, although not rigorous, there is possibility that principal component regression can borrow strength from the low rank structure of Σ, which motivates our work. [sent-34, score-0.402]
18 Even though the statistical performance of principal component regression in low dimensions is not fully understood, there is even less analysis on principal component regression in high dimensions where the dimension d can be even exponentially larger than the sample size n. [sent-35, score-0.774]
19 This is partially due to the fact that estimating the leading eigenvectors of Σ itself has been difficult enough. [sent-36, score-0.061]
20 Very recently, Han and Liu (2013b) relax the Gaussian assumption in conducting a scale invariant version of the sparse PCA (i. [sent-48, score-0.082]
21 , estimating the leading eigenvector of the correlation instead of the covariance matrix). [sent-50, score-0.095]
22 Secondly, in high dimensions where d can increase much faster, even exponentially faster, than n, we propose a robust method in conducting (sparse) principal component regression under a nonGaussian elliptical model. [sent-55, score-0.614]
23 The elliptical distribution is a semiparametric generalization to the Gaussian, relaxing the light tail and zero tail dependence constraints, but preserving the symmetry property. [sent-56, score-0.223]
24 This distribution family includes many u well known distributions such as multivariate Gaussian, rank deficient Gaussian, t, logistic, and many others. [sent-59, score-0.071]
25 Under the elliptical model, we exploit the result in Han and Liu (2013a), who showed that by utilizing a robust covariance matrix estimator, the multivariate Kendall’s tau, we can obtain an estimator u1 , which can recover u1 in the optimal parametric rate as shown in Vu and Lei (2012). [sent-60, score-0.279]
26 We then exploit u1 in conducting principal component regression and show that the obtained estiˇ mator β can estimate β in the optimal s log d/n rate. [sent-61, score-0.438]
27 2 Classical Principal Component Regression This section is devoted to the discussion on the advantage of classical principal component regression over the classical linear regression. [sent-64, score-0.481]
28 We also denote MI,J to be the submatrix of M whose rows are indexed by I and columns are indexed by J. [sent-71, score-0.068]
29 Let MI∗ and M∗J be the submatrix of M with rows indexed by I, and the submatrix of M with columns indexed by J. [sent-72, score-0.084]
30 We suppose that the following principal component regression model holds: i=1 Y = αXu1 + , (2. [sent-96, score-0.387]
31 , xn ]T ∈ Rn×d and are interested in estimating the regression coefficient β := αu1 . [sent-103, score-0.155]
32 We Let β represent the solution of the classical least square estimator without taking the information that β is proportional to u1 into account. [sent-108, score-0.137]
33 Under the principal component regression model shown in (2. [sent-114, score-0.387]
34 1 reflects the vulnerability of least square estimator on the collinearity. [sent-117, score-0.09]
35 1), the classical principal component regression estimator can be elaborated as follows. [sent-121, score-0.495]
36 (1) We first estimate u1 using the leading eigenvector u1 of the sample covariance Σ := 1 n xi xT . [sent-122, score-0.076]
37 1) by the standard least square estimation on the projected data Z := Xu1 ∈ Rn : α := (Z T Z)−1 Z T Y , The final principal component regression estimator β is then obtained as β = αu1 . [sent-124, score-0.477]
38 1, provides several important messages on the performance of principal component regression. [sent-135, score-0.277]
39 First, compared to the least square estimator β, β is insensitive to collinearity in the sense that λmin (Σ) plays no role in the rate of convergence of β. [sent-136, score-0.116]
40 These two observations, combined together, illustrate the advantages of the classical principal component regression over least square estimation. [sent-138, score-0.512]
41 These advantages justify the use of principal component regression. [sent-139, score-0.29]
42 The empirical mean square errors are plotted against 1/λd , λ1 , and α separately in (A), (B), and (C). [sent-177, score-0.068]
43 Here the results of classical linear regression and principal component regression are marked in black solid line and red dotted line. [sent-178, score-0.544]
44 3 Robust Sparse Principal Component Regression under Elliptical Model In this section, we propose a new principal component regression method. [sent-179, score-0.387]
45 We generalize the settings in classical principal component regression discussed in the last section in two directions: (i) We consider the high dimensional settings where the dimension d can be much larger than the sample size n; (ii) In modeling the predictors x1 , . [sent-180, score-0.455]
46 The elliptical family can capture characteristics such as heavy tails and tail dependence, making it more suitable for analyzing complex datasets in finance, genomics, and biomedical imaging. [sent-184, score-0.256]
47 1 Elliptical Distribution In this section we define the elliptical distribution and introduce the basic property of the elliptical d distribution. [sent-186, score-0.302]
48 To our knowledge, there are essentially four ways to define the continuous elliptical distribution with density. [sent-189, score-0.151]
49 The most intuitive way is as follows: A random vector X ∈ Rd is said to follow an elliptical distribution ECd (µ, Σ, ξ) if and only there exists a random variable ξ > 0 (a. [sent-190, score-0.151]
50 Accordingly, elliptical distribution can be regarded as a semiparametric generalization to the Gaussian distribution, with the nonparametric part ξ. [sent-195, score-0.177]
51 Because ξ can be very heavy tailed, X can also be very heavy tailed. [sent-196, score-0.104]
52 4 We would like to point out that the elliptical family is significantly larger than the Gaussian. [sent-203, score-0.168]
53 In contrast, the elliptical is a semiparametric family (since the elliptical density can be represented as g((x−µ)T Σ− 1(x−µ)) where the function g(·) function is completely unspecified. [sent-205, score-0.345]
54 2 Multivariate Kendall’s tau As a important step in conducting the principal component regression, we need to estimate u1 = Θ1 (Cov(X)) = Θ1 (Σ) as accurately as possible. [sent-209, score-0.389]
55 1) can be very heavy tailed, the according elliptical distributed random vector can be heavy tailed. [sent-211, score-0.255]
56 , 2002; Han and Liu, 2013b), the leading eigenvector of the sample covariance matrix Σ can be a bad estimator in estimating u1 = Θ1 (Σ) under the elliptical distribution. [sent-213, score-0.284]
57 In particular, in this paper we consider using the multivariate Kendall’s tau (Choi and Marden, 1998) and recently deeply studied by Han and Liu (2013a). [sent-215, score-0.1]
58 The population multivariate Kendall’s tau matrix, denoted by K ∈ Rd×d , is defined as: K := E (X − X)(X − X)T X −X 2 2 . [sent-218, score-0.1]
59 The sample version of multivariate Kendall’s tau is accordingly defined as K= 1 n(n − 1) i=j (xi − xj )(xi − xj )T , xi − xj 2 2 (3. [sent-224, score-0.118]
60 Let X ∼ ECd (µ, Σ, ξ) be a continuous distribution and K be the population multivariate Kendall’s tau statistic. [sent-231, score-0.1]
61 3 Model and Method In this section we discuss the model we build and the accordingly proposed method in conducting high dimensional (sparse) principal component regression on non-Gaussian data. [sent-242, score-0.477]
62 Similar as in Section 2, we consider the classical simple principal component regression model: Y = αXu1 + = α[x1 , . [sent-243, score-0.434]
63 Thusly, the formal model of the robust sparse principal component regression considered in this paper is as follows: Md (Y , ; Σ, ξ, s) : Y = αXu1 + , x1 , . [sent-257, score-0.443]
64 5) Then the robust sparse principal component regression can be elaborated as a two step procedure: (i) Inspired by the model Md (Y , ; Σ, ξ, s) and Proposition 3. [sent-262, score-0.466]
65 6) v∈Rd where B0 (s) := {v ∈ Rd : v 0 ≤ s} and K is the estimated multivariate Kendall’s tau matrix. [sent-264, score-0.1]
66 1, u1 is also an estimator of Θ1 (Cov(X)), whenever the covariance matrix exists. [sent-267, score-0.064]
67 5) by the standard least square estimation on the projected data Z := Xu1 ∈ Rn : α := (Z T Z)−1 Z T Y , ˇ ˇ ˇ ˇ The final principal component regression estimator β is then obtained as β = αu1 . [sent-269, score-0.477]
68 2, we show that how to estimate u1 accurately plays an important role in conducting the principal component regression. [sent-272, score-0.328]
69 Under Conditions 1 and 2, we then have the following theorem, which shows that under certain ˇ conditions, β − β 2 = OP ( s log d/n), which is the optimal parametric rate in estimating the regression coefficient (Ravikumar et al. [sent-286, score-0.129]
70 Then under Condition 1 or Condition 2 and for all random vector X such that max v∈Sd−1 , v 0 ≤2s |v T (Σ − Σ)v| = oP (1), ˇ we have the robust principal component regression estimator β satisfies that ˇ β−β s log d n = OP multivariate-t . [sent-292, score-0.45]
71 Here n = 100, d = 200, and we are interested in estimating the regression coefficient β. [sent-320, score-0.129]
72 The horizontal-axis represents the cardinalities of the estimates’ support sets and the vertical-axis represents the empirical mean square error. [sent-321, score-0.067]
73 Here from the left to the right, the minimum mean square errors for lasso are 0. [sent-322, score-0.091]
74 6 4 Experiments In this section we conduct study on both synthetic and real-world data to investigate the empirical performance of the robust sparse principal component regression proposed in this paper. [sent-325, score-0.443]
75 1 Simulation Study In this section, we conduct simulation study to back up the theoretical results and further investigate the empirical performance of the proposed robust sparse principal component regression method. [sent-331, score-0.443]
76 , ud be the eigenvectors of Σ with uj := (uj1 , . [sent-340, score-0.061]
77 The top 2 leading eigenvectors u1 , u2 of Σ are specified to be sparse with sj := √ j−1 j uj 0 and ujk = 1/ sj for k ∈ [1 + i=1 si , i=1 si ] and zero for all the others. [sent-344, score-0.098]
78 With Σ, we then consider the following four different elliptical distributions: d (Normal) X ∼ ECd (0, Σ, ζ1 ) with ζ1 = χd . [sent-353, score-0.151]
79 To show the estimation accuracy, Figure ˇ 2 plots the empirical mean square error between the estimate u1 and true regression coefficient β ˇ against the numbers of estimated nonzero entries (defined as u1 0 ), for PCR and RPCR, under different schemes of (n, d), Σ and different distributions. [sent-382, score-0.162]
80 As discussed in Section 2, especially as shown in Figure 1, linear regression and principal component regression have their own advantages in different settings. [sent-385, score-0.51]
81 For example, under the Gaussian settings with n = 100 and d = 200, the lowest mean square error for lasso is 0. [sent-387, score-0.075]
82 Moreover, when the data are indeed normally distributed, there is no obvious difference between RPCR and PCR, indicating that RPCR is a safe alternative to the classical sparse principal component regression. [sent-392, score-0.355]
83 quantile plot of the log-return values for one stock ”Goldman Sachs”. [sent-402, score-0.08]
84 2 Application to Equity Data In this section we apply the proposed robust sparse principal component regression and the other two methods to the stock price data from Yahoo! [sent-406, score-0.484]
85 We collect the daily closing prices for 452 stocks that are consistently in the S&P; 500 index between January 1, 2003 through January 1, 2008. [sent-410, score-0.067]
86 Let St = [Stt,j ] denote by the closing price of stock j on day t. [sent-412, score-0.086]
87 This is done first by conducting marginal normality tests (Kolmogorove-Smirnov, Shapiro-Wilk, and Lillifors) on the data. [sent-415, score-0.071]
88 We find that at most 24 out of 452 stocks would pass any of three normality test. [sent-416, score-0.064]
89 With Bonferroni correction there are still over half stocks that fail to pass any normality tests. [sent-417, score-0.064]
90 Moreover, to illustrate the heavy tailed issue, we plot the quantile vs. [sent-418, score-0.144]
91 It can be observed that the log return values for this stock is heavy tailed compared to the Gaussian. [sent-420, score-0.133]
92 We are interested in predicting the log return value in day t for each stock indexed by k (i. [sent-424, score-0.089]
93 , treating Ft,k as the response) using the log return values for all the stocks in day t − 1 to day t − 7 (i. [sent-426, score-0.088]
94 For each stock indexed by k, to learn the regression coefficient βk , we use Ft ∈{1,. [sent-430, score-0.177]
95 On principal components and regression: a statistical explanation of a natural phenomenon. [sent-448, score-0.184]
96 On the sample covariance matrix estimator of reduced effective rank population matrices, with applications to fPCA. [sent-453, score-0.079]
97 Sign and rank covariance matrices: statistical properties and application to principal components analysis. [sent-477, score-0.225]
98 Optimal sparse principal component analysis in high dimensional elliptical model. [sent-498, score-0.48]
99 On consistency and sparsity for principal components analysis in high dimensions. [sent-511, score-0.184]
100 Estimating the tail dependence function of an elliptical u distribution. [sent-521, score-0.174]
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