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"Frontmatter". In: Analysis of Financial Time Series

"Frontmatter". In: Analysis of Financial Time Series

"Frontmatter". In: Analysis of Financial Time Series

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DISTRIBUTIONAL PROPERTIES OF RETURNS 13f(x)0.0 0.1 0.2 0.3 0.4MixtureCauchyNormal-4 -2 0 2 4xFigure 1.1. Comparison <strong>of</strong> finite-mixture, stable, and standard normal density functions.1.2.3 Multivariate ReturnsLet r t = (r 1t ,...,r Nt ) ′ be the log returns <strong>of</strong> N assets at time t. The multivariateanalyses <strong>of</strong> Chapters 8 and 9 are concerned with the joint distribution <strong>of</strong> {r t }t=1 T .This joint distribution can be partitioned in the same way as that <strong>of</strong> Eq. (1.15). Theanalysis is then focused on the specification <strong>of</strong> the conditional distribution functionF(r t | r t−1 ,...,r 1 , θ). <strong>In</strong> particular, how the conditional expectation and conditionalcovariance matrix <strong>of</strong> r t evolve over time constitute the main subjects <strong>of</strong> Chapters 8and 9.The mean vector and covariance matrix <strong>of</strong> a random vector X = (X 1 ,...,X p ) aredefined asE(X) = µ x =[E(X 1 ),...,E(X p )] ′ ,Cov(X) = Σ x = E[(X − µ x )(X − µ x ) ′ ]provided that the expectations involved exist. When the data {x 1 ,...,x T } <strong>of</strong> X areavailable, the sample mean and covariance matrix are defined aŝµ x = 1 TT∑x t ,t=1̂Σ x = 1 TT∑(x t − ̂µ x )(x t − ̂µ x ) ′ .t=1

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