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Questions tagged [ergodic]

An ergodic dynamic system or stochastic process is one in which time averages agree with averages over the state space of the process.

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Is Autocorrelation of Posterior Samples always a problem in MCMC

I am experimenting with MCMC methods and have implemented a basic Metropolis-Hastings algorithm. One potential issue with this is that MH posterior samples are autocorrelated. I could verify that ...
44 views

Stationary Process Ergodicity

Can you give me an example of a stationary nonergodic stochastic process that is time continuous?
39 views

What is Ergodic Variance

I am curious as to the definition of ergodic variance in relation to an estimate of some parameter. It was mentioned to me by a teacher although I have not been able to find any references to it.
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What does the distribution of samples from an MCMC method converge to without repeated samples?

Suppose I have an absolutely continuous distribution with density $f(x)$ and I use an mcmc sampler which has accept/reject step to sample from this distribution. In the final samples, there are some ...
28 views

Do measurable maps preserve stationary ergodicity?

In a recent effort to establish stationary ergodicity for a certain stochastic process, I just happened to come across a statement, which I find to be little bit confounding. Given two measurable ...
26 views

Do we need ergodic-stationarity of the response variable in OLS spline regression?

I was wondering if we need the response variable to be ergodic stationarity when estimating an OLS spline regression. My intuition tells me that it's not needed but I would like to have a confirmation ...
22 views

Prior/degree of belief/degree of lack-of-information/algorithms/complexity

For a long time I had a bit of difficulty understanding what "degree of belief" means. Recently I had some thoughts about it and I wonder if they make any sense, or is there some literature about ...
23 views

Stationary and ergodic r.v: relation between error and independent variable

In time series often hold the condition that a r.v. is stationary and ergodic, allowing the application of the law of large number. If in a model as: Y= a + bX + u ...
204 views

Law of Large Numbers for Covariance Stationary Processes… Difference and Relationship between LLN and Ergodicity

We have a covariance stationary time series. We must assume that the time series was produced by an ergodic process if we are to make the bridge between the realization of the time series that we ...
26 views

Magnitude of non-ergodicity effect on the individual's risk of bankruptcy

Dr. Ole Peters presents the concept of (non-)ergodicity with the following gambling example: You're given $\$100$to play a game where you toss a coin once a minute. If it comes up heads, you win$50\...
70 views

How do I create an iid Rademacher sequence?

The lecture notes say: Let $(\Omega,\mathcal{A},P) = ((0,1],\mathcal{B}((0,1]),\lambda)$ where $\lambda$ is the Lebesgue measure on the unit interval. Define $X(\omega) = 1$ for $\omega > 1/2$ ...
883 views

Ergodicity explained in layman terms

I've been told that Ergodicity gives us a practical vision of processes WSS (Wise-sense stationary) and a bunch of integrals. For me, it is not enough to fully understand it. Could someone explain me ...
125 views

Stationary Distribution of Multiplicative Autoregressive Model

I know for the additive autoregressive model the stationary distribution of $\{X_t\}$ can be found, if it exists, in the following way: \begin{align} X_t &= \alpha X_{t-1} + \epsilon_t\\ \...
111 views

Is strict stationarity a sufficient condition for ergodicity?

For a given time series, is strict stationarity a sufficient condition for ergodicity? I am wondering if it isn't also sufficient for a time series to be weakly stationary because then the mean is a ...
309 views

How are ergodicity and “weak dependence” related?

I understand that weak dependence is a broad concept, the definition I am referring to is the one Wooldridge (2013) uses as an assumption that has to be fulfilled (amongst other assumptions) so that ...
291 views

Wide-Sense Stationary but not ergodic

This is based on example 2.2 from Machine Learning: A Bayesian and Optimization Perspective by Theodoridis. Please note that I'm not at all familiar with ergodic theory and I'm reading this with ...
59 views

Examples of ergodic process

An ergodic process is a process in which the structures of inter-individual variation and intra-individual variation are asymptotically equivalent (Molenaar, 2004). In other words: A process is non-...
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Transformations on sets of measure zero in probability space

Given a probability space $(X, \Sigma,\mu, T)$, where $\mu$ is a probability measure, $\Sigma$ is a sigma algebra on $X$, and $T$ is a transformation, then a 'measure preserving transformation' is one ...
98 views

A question about ergodic processes - 'global' vs 'local'

I have a question regarding the ergodicity of a transformation. Given a probability space, $(X,\Sigma,\mu,T_{N})$ where, $({T_{N})}_{n\geqslant 0}$ And T is some ordered transformation ...
404 views

Is there a Monte Carlo/MCMC sampler implemented which can deal with isolated local maxima of posterior distribution?

I'm currently using a bayesian approach to estimate parameters for a model consisting of several ODEs. As I have 15 parameters to estimate, my sampling space is 15-dimensional and my searched for ...
70 views

Problem involving Ergodic theorem and Markov Chain

With regards to the question in the above picture and the markov chain drawn in the question, my query is whether is it possible to conclude from Ergodic theorem that this Markov chain has an ...
136 views

ergodic theory for markov processes

For an ergodic Markov Chain $$\frac{1}{N}\sum_{i=1}^n f(X_i) \rightarrow E_\pi[f]$$ where $\pi$ is the invariant distribution. I am also dealing with a Markovian process (a state space model to ...
66 views

How do I test a (mathematical) system of equations for ergodicity?

I have a set of equations, which I can plot in for example Matlab. I would like to test for ergodicity: how can I do this? Similar questions have been asked here and here, but it is not very clear ...
120 views

Introduction to Markov Process (Part 2): Dynamical system and Markov relationship?

In my previous post asked here Introduction to Markov process: How to prove that a process is Markov? Part 1, -- a process is Markovian if it follows the memoryless property. Consider, a dynamical ...
114 views

Resource request : How to prove the output of a process is random variables?

I am reading through articles which present the spectral properties of chaotic systems such that they can be candidates for generating pseudo random binary sequences. One such article, is http://...
892 views

How to detect if Ergodicity, Stationarity and Martingale. dif. sequence?

I'm not sure, but I think I've read somewhere that because the Classical Linear Regression model assumes to have a random sample, when researchers they might not be in presence of a sample with that ...
137 views

Ergodicity of 2 independent ergodic random processes

I'm wondering if $\{X_i\}$ and $\{Y_i\}$ are 2 independent processes that are ergodic, then would $\{(X_i,Y_i)\}$ be ergodic? I believe it is the case under the additional assumption that the two ...
40 views

How long does it take two identical hidden Markov models run on same observations to forget their initial distributions (if ever)?

Let $H_1$ and $H_2$ be two instances of a finite Hidden Markov Model (HMM) $H$. That is, $H_1$ and $H_2$ have identical state spaces $Q$ as well as identical transition $A$ and emission probabilities \$...
1k views

How do I measure a speedup?

I have two versions of the same program. I apply a number of performance tests to both and measure their response time, for instance https://gist.github.com/valtih1978/d2cc2fe96fbbe1987ada ...
387 views

What does non-ergodicity mean for Bayesian statistics?

As said in the title, what would non-ergodicity mean for Bayesian satistics, and if the process being investigated is non-ergodic, how would Bayesian methods tackle this process - would it be ...
797 views

When is a ARMA(p,q) process ergodic?

We know that a ARMA(p,q) process is weakly stationary, iff there is no root of the characteristic polynomial of its AR part lying on the unit circle. But what is the necessary and sufficient ...
127 views

Metropolis Ergodicity

I have encountered one last problem with regarding to the Metropolis-Hastings algorithm. I know that ergodicity is needed in the algorithm to imply convergence to a unique stationary distribution. But ...
727 views

How do you check ergodicity of a stochastic processes from its sample path(s)?

How do you check ergodicity of a wide-sense stationary stochastic processes from its sample path(s)? Can we check ergodicity from a single sample path? Or do we need multiple sample paths? One ...
849 views

Derivation of sample autocovariance

The autocovariance is defined as $$\gamma(t,s) = Cov(X_{t}, X_{s})=E[(X_{t}-\mu_{t})(X_{s}-\mu_{s})]$$ When we have a stationary process the only thing that matters is the lag between the variables: ...
346 views

Is it necessary to check ergodicity in estimation of autocorrelation function?

Given a sample path from a process supposed to be stationary, I saw the sample autocorrelation function of the sample path is used to estimate the autocorrelation function of the process. But this ...