3
3.1. . 1
3.2. - . 5
3.3. . 12
3.4. TS - DS -. 19
3.5. - ARFIMA.. 27
3.5.1. . 28
3.5.2. ARFIMA.. 33
3.5.3. ARFIMA.. 42
3.5.4 .. 50
3.5.5 ARFIMA.. 52
, t t - l (l - ) . , , . , , , , . , . , ARIMA ARFIMA ( ). (TS -) (DS -). , , . [1-15].
(random walk) . () , . .
, - . . , , , .
Xt = Xt 1 + at, (3.1)
, , at - .
.3.1 , . 0 , .
.3.1.
.3.2 (3.1), , AR (1).
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) )
.3.2. () ()
AR (1) Xt 1, , ..
Xt = 1 Xt - 1 + at,
1 = 1.
AR (1) , ׀ 1 ׀< 1. 1, , , 1 =1,1 1 =1,5. .3.3 AR (1) 1 ( at ). , , , , .. .
1 =1,1 1 =1,5
.3.3. AR (1) 1 =1,1 1 =1,5
, , (3.1) .
AR (1) ( 1)
Xt - Xt - 1 = 1 Xt - 1 - Xt - 1 + at = ( 1 -1) Xt - 1 + at Δ Xt = φ Xt - 1 + at,
Δ Xt = Xt - Xt - 1; φ = 1 -1.
1 = 1 φ = 1 - 1 = 0, Δ Xt Xt , () Δ Xt () Xt - 1 = t - 1 t - 1 . , Xt - 1 = t - 1 Xt = Δ Xt + Xt - 1 t - 1 . at ( ), Xt = t , t - 1. .
1 > 1 φ = 1 - 1 > 0, Δ Xt () Xt - 1 = t - 1 , (Δ Xt | Xt - 1 = t - 1 ) = φ t - 1, , t - 1. , t - 1 > 0, Xt = t t - 1; t - 1 < 0 Xt = t t - 1. .
(3.1),
Xt = Xt - 1 + at = (Xt - 2 + at - 1) + at = Xt - 2 + at - 1 + at = (Xt - 3 + at - 2) + at - 1 + at =
= Xt - 3 + at - 2 + at - 1 + at =... = X 0 + (a 1 +... + at),
..
X 0 = 0 - .
:
E (Xt | X 0 = 0) = 0,
D (Xt | X 0 = 0) = D (a 1 +... + at) = D (a 1 ) +... + D (at) = t D (a 1) = t σ a 2.
, (3.1) , , .
(3.1) , , .. Δ Xt = Xt - Xt 1 = (1 ) Xt. Δ Xt = at. , (3.1) . .3.4.
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.3.4.
, . , .. d ARMA [2].