15. SMC algorithm (ブートストラップ・フィル
ター)
1 Set ZN
0
← 1, sample 𝜉1
0
∼ M(dx0) for i ∈ {1, ..., N},
set
𝜂N
0 =
1
N
N
Õ
i=1
𝛿𝜉i
0
(1)
2 For p = 1, .., n, set ZN
p ← ZN
p−1
1
N
ÍN
i Gp−1(𝜉i
p−1
),
sample
𝜉i
p ∼
ÍN
i=1 Gp−1(𝜉i
p−1
)Mp(𝜉i
p−1
, ·)
ÍN
j=1 Gp−1(𝜉j
p−1
)
(2)
and set 𝜂N
p ← 1
N
ÍN
i=1 𝛿𝜉i
p
, 𝛾N
p ← ZN
p 𝜂N
p
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16. To simulate 𝜉i
p ∼
ÍN
i=1 Gp−1(𝜉i
p−1
)Mp(𝜉i
p−1
,·)
ÍN
j=1 Gp−1(𝜉
j
p−1
)
1 For i ∈ {1, .., N}, sample independently
Ai
p ∼ Categorical(Gp−1(𝜉1
p−1), ..., Gp−1(𝜉N
p−1)) (3)
2 For i ∈ {1, .., N}, sample independently
𝜉i
p ∼ Mp(𝜉
Ai
p−1
p−1
, ·)
• Ai
p−1
は 𝜉i
p の ancestor index と呼ばれることもある.
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17. Ancestor index
Figure: p = 3, N = 4 の ancestor index の例.
A3 = (3, 2, 2, 3), A2 = (2, 2, 2, 4), A1 = (1, 2, 4, 4).
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18. SMC estimators
1 E(𝛾N
p (𝜙)) = 𝛾p(𝜙): 不偏性 (𝜂 も)
2 N → ∞ で 𝛾N
p (𝜙) → 𝛾p(𝜙), w.p.1: 一致性 (𝜂 も)
3 N → ∞ で
p
(N)(
𝛾N
p (𝜙)−𝛾p (𝜙)
𝛾p (1) ) → N (0, 𝜎2
p (𝜙)):
CLT(𝜂 も)
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