Probability and expected number of steps of/from a transient to an absorbing state in a Markov Chain












3












$begingroup$


Given an arbitrary but relatively large (more than 50 states) transition matrix, the goal is to find the answer to the following problem:




Assuming we start at state A and ultimately end up in (the only)
absorbing state Z we are looking for a state S that follows:



A → [m steps] → S → [n steps] → Z




How can I calculate the probability of reaching S before reaching Z and the corresponding expected number of steps (n) from S to Z?



Update 24-12:



So I guess the first part is mosre doable than i thought (if my reasoning is correct). My approach:





  1. Rearrange the matrix in canonical form:




    $P = left[begin{matrix}
    Q & R \ mathbf{0} & I
    end{matrix}right]$





  2. Find the fundamental matrix:




    $ N = (I - Q)^{-1} $





  3. Find the transient probabilities:




    $ H = (N - I)N_{dg} $




  4. And the row of H which corresponds to starting state A. The entries in this row vector should correspond to the probabilities of reaching A before reaching Z.



** Is my thinking here correct? And how can I condition the original transition matrix P to estimate the steps (n) between A and Z? **










share|cite|improve this question











$endgroup$












  • $begingroup$
    To clarify, we have a starting state A, ending state Z, and want to find a state S such that, conditioned on passing through S, the expected value of the number of steps to get to S is m, the the number of steps to get to Z is n?
    $endgroup$
    – Alex
    Dec 23 '18 at 3:10










  • $begingroup$
    Yes, exactly! I just don't exactly how to approach such calculation.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:00












  • $begingroup$
    My idea would be that this problem is two-fold: 1. Find the probability of reaching S before absorption, and then 2. Transforming the matrix to the conditional probability as you say. But honestly I don't know exactly how to approach either.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:06












  • $begingroup$
    Are you looking for the probability distribution of the time to absorption for finite discrete or continuous time Markov chain?
    $endgroup$
    – Waqas
    Dec 28 '18 at 12:31
















3












$begingroup$


Given an arbitrary but relatively large (more than 50 states) transition matrix, the goal is to find the answer to the following problem:




Assuming we start at state A and ultimately end up in (the only)
absorbing state Z we are looking for a state S that follows:



A → [m steps] → S → [n steps] → Z




How can I calculate the probability of reaching S before reaching Z and the corresponding expected number of steps (n) from S to Z?



Update 24-12:



So I guess the first part is mosre doable than i thought (if my reasoning is correct). My approach:





  1. Rearrange the matrix in canonical form:




    $P = left[begin{matrix}
    Q & R \ mathbf{0} & I
    end{matrix}right]$





  2. Find the fundamental matrix:




    $ N = (I - Q)^{-1} $





  3. Find the transient probabilities:




    $ H = (N - I)N_{dg} $




  4. And the row of H which corresponds to starting state A. The entries in this row vector should correspond to the probabilities of reaching A before reaching Z.



** Is my thinking here correct? And how can I condition the original transition matrix P to estimate the steps (n) between A and Z? **










share|cite|improve this question











$endgroup$












  • $begingroup$
    To clarify, we have a starting state A, ending state Z, and want to find a state S such that, conditioned on passing through S, the expected value of the number of steps to get to S is m, the the number of steps to get to Z is n?
    $endgroup$
    – Alex
    Dec 23 '18 at 3:10










  • $begingroup$
    Yes, exactly! I just don't exactly how to approach such calculation.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:00












  • $begingroup$
    My idea would be that this problem is two-fold: 1. Find the probability of reaching S before absorption, and then 2. Transforming the matrix to the conditional probability as you say. But honestly I don't know exactly how to approach either.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:06












  • $begingroup$
    Are you looking for the probability distribution of the time to absorption for finite discrete or continuous time Markov chain?
    $endgroup$
    – Waqas
    Dec 28 '18 at 12:31














3












3








3





$begingroup$


Given an arbitrary but relatively large (more than 50 states) transition matrix, the goal is to find the answer to the following problem:




Assuming we start at state A and ultimately end up in (the only)
absorbing state Z we are looking for a state S that follows:



A → [m steps] → S → [n steps] → Z




How can I calculate the probability of reaching S before reaching Z and the corresponding expected number of steps (n) from S to Z?



Update 24-12:



So I guess the first part is mosre doable than i thought (if my reasoning is correct). My approach:





  1. Rearrange the matrix in canonical form:




    $P = left[begin{matrix}
    Q & R \ mathbf{0} & I
    end{matrix}right]$





  2. Find the fundamental matrix:




    $ N = (I - Q)^{-1} $





  3. Find the transient probabilities:




    $ H = (N - I)N_{dg} $




  4. And the row of H which corresponds to starting state A. The entries in this row vector should correspond to the probabilities of reaching A before reaching Z.



** Is my thinking here correct? And how can I condition the original transition matrix P to estimate the steps (n) between A and Z? **










share|cite|improve this question











$endgroup$




Given an arbitrary but relatively large (more than 50 states) transition matrix, the goal is to find the answer to the following problem:




Assuming we start at state A and ultimately end up in (the only)
absorbing state Z we are looking for a state S that follows:



A → [m steps] → S → [n steps] → Z




How can I calculate the probability of reaching S before reaching Z and the corresponding expected number of steps (n) from S to Z?



Update 24-12:



So I guess the first part is mosre doable than i thought (if my reasoning is correct). My approach:





  1. Rearrange the matrix in canonical form:




    $P = left[begin{matrix}
    Q & R \ mathbf{0} & I
    end{matrix}right]$





  2. Find the fundamental matrix:




    $ N = (I - Q)^{-1} $





  3. Find the transient probabilities:




    $ H = (N - I)N_{dg} $




  4. And the row of H which corresponds to starting state A. The entries in this row vector should correspond to the probabilities of reaching A before reaching Z.



** Is my thinking here correct? And how can I condition the original transition matrix P to estimate the steps (n) between A and Z? **







markov-chains conditional-probability






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 24 '18 at 22:19







Remy Kabel

















asked Dec 19 '18 at 8:45









Remy KabelRemy Kabel

735




735












  • $begingroup$
    To clarify, we have a starting state A, ending state Z, and want to find a state S such that, conditioned on passing through S, the expected value of the number of steps to get to S is m, the the number of steps to get to Z is n?
    $endgroup$
    – Alex
    Dec 23 '18 at 3:10










  • $begingroup$
    Yes, exactly! I just don't exactly how to approach such calculation.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:00












  • $begingroup$
    My idea would be that this problem is two-fold: 1. Find the probability of reaching S before absorption, and then 2. Transforming the matrix to the conditional probability as you say. But honestly I don't know exactly how to approach either.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:06












  • $begingroup$
    Are you looking for the probability distribution of the time to absorption for finite discrete or continuous time Markov chain?
    $endgroup$
    – Waqas
    Dec 28 '18 at 12:31


















  • $begingroup$
    To clarify, we have a starting state A, ending state Z, and want to find a state S such that, conditioned on passing through S, the expected value of the number of steps to get to S is m, the the number of steps to get to Z is n?
    $endgroup$
    – Alex
    Dec 23 '18 at 3:10










  • $begingroup$
    Yes, exactly! I just don't exactly how to approach such calculation.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:00












  • $begingroup$
    My idea would be that this problem is two-fold: 1. Find the probability of reaching S before absorption, and then 2. Transforming the matrix to the conditional probability as you say. But honestly I don't know exactly how to approach either.
    $endgroup$
    – Remy Kabel
    Dec 23 '18 at 11:06












  • $begingroup$
    Are you looking for the probability distribution of the time to absorption for finite discrete or continuous time Markov chain?
    $endgroup$
    – Waqas
    Dec 28 '18 at 12:31
















$begingroup$
To clarify, we have a starting state A, ending state Z, and want to find a state S such that, conditioned on passing through S, the expected value of the number of steps to get to S is m, the the number of steps to get to Z is n?
$endgroup$
– Alex
Dec 23 '18 at 3:10




$begingroup$
To clarify, we have a starting state A, ending state Z, and want to find a state S such that, conditioned on passing through S, the expected value of the number of steps to get to S is m, the the number of steps to get to Z is n?
$endgroup$
– Alex
Dec 23 '18 at 3:10












$begingroup$
Yes, exactly! I just don't exactly how to approach such calculation.
$endgroup$
– Remy Kabel
Dec 23 '18 at 11:00






$begingroup$
Yes, exactly! I just don't exactly how to approach such calculation.
$endgroup$
– Remy Kabel
Dec 23 '18 at 11:00














$begingroup$
My idea would be that this problem is two-fold: 1. Find the probability of reaching S before absorption, and then 2. Transforming the matrix to the conditional probability as you say. But honestly I don't know exactly how to approach either.
$endgroup$
– Remy Kabel
Dec 23 '18 at 11:06






$begingroup$
My idea would be that this problem is two-fold: 1. Find the probability of reaching S before absorption, and then 2. Transforming the matrix to the conditional probability as you say. But honestly I don't know exactly how to approach either.
$endgroup$
– Remy Kabel
Dec 23 '18 at 11:06














$begingroup$
Are you looking for the probability distribution of the time to absorption for finite discrete or continuous time Markov chain?
$endgroup$
– Waqas
Dec 28 '18 at 12:31




$begingroup$
Are you looking for the probability distribution of the time to absorption for finite discrete or continuous time Markov chain?
$endgroup$
– Waqas
Dec 28 '18 at 12:31










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