Academia.edu no longer supports Internet Explorer.
To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser.
Bayesian Time Series Models
AI
Adaptive Markov chain Monte Carlo (MCMC) methods enhance sampling efficiency from arbitrary distributions by automating the adjustment of transition probabilities. The paper identifies the challenges in finding optimal proposal distributions and presents adaptive algorithms, specifically the adaptive Metropolis method, which updates sampling parameters dynamically based on previous iterations to optimize convergence rates. Through comparisons with traditional techniques, the study demonstrates that adaptive methods can significantly improve performance in high-dimensional contexts.
2020
Note this is a random variable with expected value π(f) (i.e. the estimator is unbiased) and standard deviation of order O(1/ √ N). Then by CLT, the errorπ(f) − π(f) will have a limiting normal distribution as N → ∞. Therefore we can compute π(f) by computing samples (plus some regression techniques?). But the problem is if π u is complicated, then it is very difficult to simulate i.i.d. random variables from π(•). The MCMC solution is to construct a Markov chain on X which has π(•) as a stationary distribution, i.e. X π(dx)P (x, dy) = π(dy) Then for large n the distribution of X n will be approximately stationary. We can set Z 1 = X n and get Z 2 , Z 3 ,. .. , Z n repeatedly. Remark. In practice instead of starting a fresh Markov chain every time we take the successive X n 's, for example, (N − B) −1 N i=B+1 f (X i). We tend to ignore the dependence problem as many of the mathematical issues are similar in either implementation. Remark. We have other ways of estimation, such as "rejection sampling" and "importance sampling". But MCMC algorithms is applied most widely. 2 MCMC and its construction This section will explain how MCMC algorithm is constructed. Now we introduce reversibility. Definition. A Markov Chain on state space X is reversible with respect to a probability distribution π(•) on X , if π(dx)P (x, dy) = π(dy)P (y, dx), x, y ∈ X Proposition. A Markov Chain is reversible with respect to π(•), then π(•) is the stationary distribution for the chain. Proof. By reversibility, we have x∈X π(dx)P (x, dy) = x∈X π(dy)P (y, dx) = π(dy) x∈X P (x, dy) = π(dy) Now the simplest way to construct a MCMC algorithm which satisfies reversibility is using Metropolis-Hastings algorithm. 2.1 The Metropolis-Hastings Algorithm. Suppose that π(•) has a (possibly unnormalized) density π u. Let Q(x, •) be essentially any other Markov Chain, whose transitions also have a (possibly unnormalized) density, i.e. Q(x, dy) ∝ q(x, y)dy. First choose some X 0. Then given X n , generate a proposal Y n+1 from Q(X n , •). In the meantime we flip a independent bias coin with probability of heads equals to α(X n , Y n+1), where α(x, y) = min 1, π u (y)q(y, x) π u (x)q(x, y) , π(x)q(x, y) = 0 And α(x, y) = 1 when π(x)q(x, y) = 0. Then if the coin is heads, we accept the proposal and set X n+1 = Y n+1. If the coin is tails, then we reject the proposal and set X n+1 = X n. Then we replace n by n + 1 and repeat. The reason we take α(x, y) as above is explain as follow. Proposition. The Metropolis-Hastings Algorithm produces a Markov Chain {X n } which is reversible with respect to π(•). Proof. We want to show for any x, y ∈ X , π(dx)P (x, dy) = π(dy)P (y, dx) whereȲ i = 1 J j Y ij. The Gibbs sampler then proceeds by updating the K + 3 variables according to the above conditional distributions. This is feasible since the conditional distributions are all easily simulated (IG and N).
The Annals of Statistics, 2011
Adaptive and interacting Markov chain Monte Carlo algorithms (MCMC) have been recently introduced in the literature. These novel simulation algorithms are designed to increase the simulation efficiency to sample complex distributions. Motivated by some recently introduced algorithms (such as the adaptive Metropolis algorithm and the interacting tempering algorithm), we develop a general methodological and theoretical framework to establish both the convergence of the marginal distribution and a strong law of large numbers. This framework weakens the conditions introduced in the pioneering paper by Roberts and Rosenthal [J. Appl. Probab. 44 (2007) 458-475]. It also covers the case when the target distribution π is sampled by using Markov transition kernels with a stationary distribution that differs from π .
Proceeding of the 2001 Winter Simulation Conference (Cat. No.01CH37304), 2001
This paper discusses some connections between adaptive Monte Carlo algorithms and general state space Markov chains. Adaptive algorithms are iterative methods in which previously generated samples are used to construct a more efficient sampling distribution at the current iteration. In this paper, we describe two such adaptive algorithms, one arising in a finite-horizon computation of expected reward and the other arising in the context of solving eigenvalue problems. We then discuss the connection between these adaptive algorithms and general state space Markov chain theory, and offer some insights into some of the technical difficulties that arise in trying to apply the known theory for general state space chains to such adaptive algorithms.
Resonance, 2003
In this report, we propose an original approach to solve Fredholm equations of the second kind. We interpret the standard von Neumann expansion of the solution as an expectation with respect to a probability distribution de…ned on an union of subspaces of variable dimension. Based on this representation, it is possible to use trans-dimensional Markov Chain Monte Carlo (MCMC) methods such as Reversible Jump MCMC to approximate the solution numerically. This can be an attractive alternative to standard Sequential Importance Sampling (SIS) methods routinely used in this context. We sketch an application to value function estimation for a Markov decision process.
American Journal of Physics, 2016
Markov chain Monte Carlo algorithms are invaluable tools for exploring stationary properties of physical systems, especially in situations where direct sampling is unfeasible. Common implementations of Monte Carlo algorithms employ reversible Markov chains. Reversible chains obey detailed balance and thus ensure that the system will eventually relax to equilibrium, though detailed balance is not necessary for convergence to equilibrium. We review nonreversible Markov chains, which violate detailed balance and yet still relax to a given target stationary distribution. In particular cases, nonreversible Markov chains are substantially better at sampling than the conventional reversible Markov chains with up to a square root improvement in the convergence time to the steady state. One kind of nonreversible Markov chain is constructed from the reversible ones by enlarging the state space and by modifying and adding extra transition rates to create non-reversible moves. Because of the au...
Monte Carlo and Quasi-Monte Carlo Methods 2008, 2009
We study the convergence behavior of a randomized quasi-Monte Carlo (RQMC) method for the simulation of discrete-time Markov chains, known as array-RQMC. The goal is to estimate the expectation of a smooth function of the sample path of the chain. The method simulates n copies of the chain in parallel, using highly uniform point sets randomized independently at each step. The copies are sorted after each step, according to some multidimensional order, for the purpose of assigning the RQMC points to the chains. In this paper, we provide some insight on why the method works, explain what would need to be done to bound its convergence rate, discuss and compare different ways of realizing the sort and assignment, and report empirical experiments on the convergence rate of the variance and of the mean square discrepancy between the empirical and theoretical distribution of the states, as a function of n, for various types of discrepancies.
arXiv (Cornell University), 2013
In this paper we study Markov chains associated with the Metropolis-Hastings algorithm. We consider conditions under which the sequence of the successive densities of such a chain converges to the target density according to the total variation distance for any choice of the initial density. In particular we prove that the positiveness of the proposal density is enough for the chain to converge. The content of this work basically presents a stand alone proof that the reversibility along with the kernel positivity imply the convergence.
2014
We have shown here that geometric ergodicity is achieved for sub-exponential targets for two versions of TMCMC- the additive and the additive-multiplicative hybrid TMCMC schemes. Also, we obtain the optimal scaling by maximizing the diffusion speed of the limiting time-scaled diffusion process for TMCMC. We show that the optimal acceptance rate is 0.439 for TMCMC which is almost twice as large as RWMH (0.234). We observe that convergence to stationarity for TMCMC is faster than RWMH but the mixing property in RWMH is relatively better. However TMCMC is more robust with respect to scaling and dimensionality. This is attested by simulation runs on Gaussian and nearest neighbor models.
2017
Markov Chain Monte Carlo methods are often used for analyzing a large, highly dimensional state space, with which there are two primary applications: 1. Approximating the expected value of a posterior distribution 2. Sampling values that approximately follow the stationary distribution of a Markov Chain In both cases, the distribution being sampled is often a multi-dimensional integral. While constructing a Markov Chain and implementing one of several random walk algorithms isn’t considered to be di cult, there a large area of research that exists exploring how to reduce the number of steps/computational cost required to converge to the stationary distribution of the Markov Chain within some level of error. When an MCMC sampling method converges in distribution1 quickly, the chain is said to have rapid mixing. Mark Chain Monte Carlo methods that exhibit rapid mixing for many general Markov Chains are often used in computer science to approximate solutions to several problems, some o...
Journal of The Royal Statistical Society Series B-statistical Methodology, 2003
Summary. The major implementational problem for reversible jump Markov chain Monte Carlo methods is that there is commonly no natural way to choose jump proposals since there is no Euclidean structure in the parameter space to guide our choice. We consider mechanisms for guiding the choice of proposal. The first group of methods is based on an analysis of acceptance probabilities for jumps. Essentially, these methods involve a Taylor series expansion of the acceptance probability around certain canonical jumps and turn out to have close connections to Langevin algorithms. The second group of methods generalizes the reversible jump algorithm by using the so-called saturated space approach. These allow the chain to retain some degree of memory so that, when proposing to move from a smaller to a larger model, information is borrowed from the last time that the reverse move was performed. The main motivation for this paper is that, in complex problems, the probability that the Markov chain moves between such spaces may be prohibitively small, as the probability mass can be very thinly spread across the space. Therefore, finding reasonable jump proposals becomes extremely important. We illustrate the procedure by using several examples of reversible jump Markov chain Monte Carlo applications including the analysis of autoregressive time series, graphical Gaussian modelling and mixture modelling.
Computational Statistics, 2021
We consider versions of the Metropolis algorithm which avoid the inefficiency of rejections. We first illustrate that a natural Uniform Selection Algorithm might not converge to the correct distribution. We then analyse the use of Markov jump chains which avoid successive repetitions of the same state. After exploring the properties of jump chains, we show how they can exploit parallelism in computer hardware to produce more efficient samples. We apply our results to the Metropolis algorithm, to Parallel Tempering, to a Bayesian model, to a two-dimensional ferromagnetic 4×4 Ising model, and to a pseudomarginal MCMC algorithm.
Esaim: Proceedings, 2007
In this paper we introduce a class of non-linear Markov Chain Monte Carlo (MCMC) methods for simulating from a probability measure π. Non-linear Markov kernels (e.g. Del Moral (2004)) can be constructed to admit π as an invariant distribution and have typically superior mixing properties to ordinary (linear) MCMC kernels. However, such non-linear kernels often cannot be simulated exactly, so, in the spirit of particle approximations of Feynman-Kac formulae (Del Moral 2004), we construct approximations of the non-linear kernels via Self-Interacting Markov Chains (Del Moral & Miclo 2004) (SIMC). We present several non-linear kernels and investigate the performance of our approximations with some simulations.
1999
This paper is concerned with improving the performance of Markov chain algorithms for Monte Carlo simulation. We propose a new algorithm for simulating from multivariate Gaussian densities. This algorithm combines ideas from Metropolis-coupled Markov chain Monte Carlo methods and from an existing algorithm based only on over-relaxation. The speed of convergence of the proposed and existing algorithms can be measured by the spectral radius of certain matrices. We present examples in which the proposed algorithm converges faster than the existing algorithm and the Gibbs sampler. We also derive an expression for the asymptotic variance of any linear combination of the variables simulated by the proposed algorithm. From this expression it follows that the proposed algorithm o ers no asymptotic variance reduction compared with the existing algorithm. We extend the proposed algorithm to the non-Gaussian case and discuss its performance by means of examples from Bayesian image analysis. We nd that better performance is obtained from a special case of the proposed algorithm, which is a modi ed version of the algorithm of , than from a Metropolis algorithm. 1 2. estimating expected values under of functions de ned over the state space.
1997
We study the slice sampler, a method of constructing a reversible Markov chain with a specified invariant distribution. Given an independence Metropolis-Hastings algorithm it is always possible to construct a slice sampler that dominates it in the Peskun sense. This means that the resulting Markov chain produces estimates with a smaller asymptotic variance. Furthermore the slice sampler has a smaller second-largest eigenvalue than the corresponding independence MetropolisHastings algorithm. This ensures faster convergence to the distribution of interest. A sufficient condition for uniform ergodicity of the slice sampler is given and an upper bound for the rate of convergence to stationarity is provided. Keywords: Auxiliary variables, Slice sampler, Peskun ordering, Metropolis-Hastings algorithm, Uniform ergodicity. 1 Introduction The slice sampler is a method of constructing a reversible Markov transition kernel with a given invariant distribution. Auxiliary variables ar...
Brazilian Journal of Probability and Statistics, 2017
We consider the recently introduced Transformation-based Markov Chain Monte Carlo (TMCMC) (Stat. Methodol. 16 (2014) 100-116), a methodology that is designed to update all the parameters simultaneously using some simple deterministic transformation of a one-dimensional random variable drawn from some arbitrary distribution on a relevant support. The additive transformation based TMCMC is similar in spirit to random walk Metropolis, except the fact that unlike the latter, additive TMCMC uses a single draw from a one-dimensional proposal distribution to update the high-dimensional parameter. In this paper, we first provide a brief tutorial on TMCMC, exploring its connections and contrasts with various available MCMC methods. Then we study the diffusion limits of additive TMCMC under various setups ranging from the product structure of the target density to the case where the target is absolutely continuous with respect to a Gaussian measure; we also consider the additive TMCMC within Gibbs approach for all the above setups. These investigations lead to appropriate scaling of the onedimensional proposal density. We also show that the optimal acceptance rate of additive TMCMC is 0.439 under all the aforementioned setups , in contrast with the well-established 0.234 acceptance rate associated with optimal random walk Metropolis algorithms under the same setups. We also elucidate the ramifications of our results and clear advantages of additive TMCMC over random walk Metropolis with ample simulation studies and Bayesian analysis of a real, spatial dataset with which 160 unknowns are associated.
Physical Review E, 2008
We demonstrate the use of a variational method to determine a quantitative lower bound on the rate of convergence of Markov chain Monte Carlo ͑MCMC͒ algorithms as a function of the target density and proposal density. The bound relies on approximating the second largest eigenvalue in the spectrum of the MCMC operator using a variational principle and the approach is applicable to problems with continuous state spaces. We apply the method to one dimensional examples with Gaussian and quartic target densities, and we contrast the performance of the random walk Metropolis-Hastings algorithm with a "smart" variant that incorporates gradient information into the trial moves, a generalization of the Metropolis adjusted Langevin algorithm. We find that the variational method agrees quite closely with numerical simulations. We also see that the smart MCMC algorithm often fails to converge geometrically in the tails of the target density except in the simplest case we examine, and even then care must be taken to choose the appropriate scaling of the deterministic and random parts of the proposed moves. Again, this calls into question the utility of smart MCMC in more complex problems. Finally, we apply the same method to approximate the rate of convergence in multidimensional Gaussian problems with and without importance sampling. There we demonstrate the necessity of importance sampling for target densities which depend on variables with a wide range of scales.
2000
Markov chain Monte Carlo (MCMC) methods have become popular as a basis for drawing inference from complex statistical models. Two common di culties with MCMC algorithms are slow convergence and long run-times, which are often closely related. Algorithm convergence can often be aided by careful tuning of the chain's transition kernel. In order to preserve the algorithm's stationary distribution, however, care must be taken when updating a chain's transition kernel based on that same chain's history. In this paper we introduce a technique that allows the transition kernel to be updated at user speci ed intervals, while preserving the chain's stationary distribution. This technique may be bene cial in aiding both the rate of convergence (by allowing adaptation of the transition kernel) and the speed of computing. The approach is particularly helpful when calculation of the full conditional (for a Gibbs algorithm) or of the candidate distribution (for a Metropolis-Hastings algorithm) is computationally expensive.
Sadhana, 2006
Markov Chain Monte Carlo (MCMC) is a popular method used to generate samples from arbitrary distributions, which may be specified indirectly. In this article, we give an introduction to this method along with some examples.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.