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arXiv 1507.03263math.STstat.TH
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高频数据分解的非参数贝叶斯方法

A non-parametric Bayesian approach to decompounding from high frequency data

Shota Gugushvili, Frank van der Meulen, Peter Spreij

摘要:

给定一个离散观测的复合泊松过程的样本,我们考虑其跳跃大小的密度$f_0$的非参数估计,以及它的强度$λ_0.$的非参数估计。我们采用贝叶斯方法来解决这个问题,并指定$f_0$的先验为正态密度的Dirichlet位置混合。假设$λ_0$的一个独立先验是紧支撑的,并且相对于Lebesgue测度具有正密度。我们表明,在适当的假设下,后验合同对$(λ_0,f_0)$在本质上(对数因子)的$\sqrt{nΔ}$率,其中$n$是观察的数量和$Δ$是网格大小的过程中进行采样。重点是高频数据,$Δ\to 0$,但所获得的结果也适用于固定的$Δ$。在这两种情况下,我们假设$nΔ\rightarrow\infty$。我们的主要结果意味着存在以相同速率收敛(在频率论意义上,在概率上)到$(λ_0,f_0)$的贝叶斯点估计。我们还讨论了我们的方法的实际实施。计算问题的处理包括辅助变量,我们开发了一个马尔可夫链蒙特卡罗算法,样本从联合分布的未知参数的混合密度和引入的辅助变量。数值例子说明了这种方法的可行性。

英文摘要:

Given a sample from a discretely observed compound Poisson process, we consider non-parametric estimation of the density $f_0$ of its jump sizes, as well as of its intensity $λ_0.$ We take a Bayesian approach to the problem and specify the prior on $f_0$ as the Dirichlet location mixture of normal densities. An independent prior for $λ_0$ is assumed to be compactly supported and to possess a positive density with respect to the Lebesgue measure. We show that under suitable assumptions the posterior contracts around the pair $(λ_0,f_0)$ at essentially (up to a logarithmic factor) the $\sqrt{nΔ}$-rate, where $n$ is the number of observations and $Δ$ is the mesh size at which the process is sampled. The emphasis is on high frequency data, $Δ\to 0$, but the obtained results are also valid for fixed $Δ$. In either case we assume that $nΔ\rightarrow\infty$. Our main result implies existence of Bayesian point estimates converging (in the frequentist sense, in probability) to $(λ_0,f_0)$ at the same rate. We also discuss a practical implementation of our approach. The computational problem is dealt with by inclusion of auxiliary variables and we develop a Markov Chain Monte Carlo algorithm that samples from the joint distribution of the unknown parameters in the mixture density and the introduced auxiliary variables. Numerical examples illustrate the feasibility of this approach.

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