() , . .
. 50- . [8]. , , . ( , 800- ) . , , . ( ) ( ). , , .
. . , . - , E ( t) = μ γ(h)= Cov (Xt, Xt + h) t. : , ࠠ
(3.22)
.
(3.22) :
(3.23)
, , ,
(3.24)
d - ; L 1(h) - .
:
L (h) = log x; L (h) = log(log x); L (h) = 1/log x.
, ARMA, .
. t , ()
. (3.25)
S (f) - 2π. , t ,
(3.26)
.. .
|
|
(3.27)
- .
.3.21 , 3329 .
.3.21.
. , , , .3.22 3.23, . , , , 200 , : h = 200 75% . .
.3.22.
.3.23.
[10]. , ,
Yt = m (t) + Xt, (3.28)
Xt - .
, m (t), , , . m (t):
(3.29)
, m (t) - ,
, m (t) = A costω0 + B sintω0, d μi(ω) = 0, ω ≠ ω0, i = 1, 2. , m (t) ω0 d μ(ω) , .
, m (t) , , . , m (t) t, ..
m (t) - , , . , , , .
, m (t) , , , , d μ(ω) (3.29) ω ≠ 0. . .
.3.24 . , , , , , , - .
.3.24 -
.3.5.
3.5
|
|
C | |
648,90 | |
11,28 | |
360,88 | |
83,56 | |
651,11 | |
423949,51 | |
0,28 | |
1,27 | |
2449,98 | |
38,53 | |
2487,98 | |
2160205,21 | |
3329 |
ARFIMA
, , .. .
Xt ARFIMA (p, d, q), (3.3)
()(1 B) d Xt = θ() at.
d , , ARFIMA (p, d, q) . [9,11], . , , , [13].
, d H, . H - ., .
:
H = 0,5;
0 < H < 0,5;
0,5 < < 1,0.
H = 0,5 . , . H 0,5 , . . , "". , . , , . , , . , , .
0 < H < 0,5 . " ". , , , . , , . , . , , -.
0,5 < < 1,0 - . () , , , - . (100% ). 0,5, . , , ( ), .
[11], d
d = H - 0,5. (3.30)
d . , , , .. f -2. . () () . :
|
|
1. H ( 0 < H < 1) (0,5 H)- .
2. f -2 H -1.
3. (k ).
[13]. ( ) f 0 , f -2. : , f -1? . f -2, , f -1. , .
ARIMA (0,1,0),
(1 B) Xt = at. (3.31)
{ Xt } , .. Xt - Xt - 1 = at. H ꠠ (0,5 H)- - . , , . (1 B) d
.
(1 B) d = 1 dB (1/2) d (1 d) B 2 (1/6) d (1 d) (2 d) B 3 - (3.32)
, - H Xt = (1 B)- d at (1 B) d Xt = at.
{ Xt } ARFIMA (0, d,0) - d.
ARFIMA (0, d,0),
(1 B) d Xt = at, (3.33)
at - , , .
{ Xt } ARFIMA (0, d,0). [11] .
1. d < 0,5 { Xt }
(3.34)
k → ∞
2. d > - 0,5 { Xt }
(3.35)
k → ∞
, .3, 4 , -0,5 < d < 0,5.
3. { Xt }
S (ω) = (2sin 0,5 ω)-2 d 0 < ω ≤ π,
S (ω) ~ ω-2 d ω → 0.
4. { Xt }
|
|
, γ0 = (-2 d)! / [(- d)!]2 ρ1 = d / (1 d).
k → ∞ (3.36)
ARFIMA (0, d,0) , d [-1/2, 1/2], , . , .
0 < d < 1/2 ARFIMA (0, d,0) . . .
d = 0 ARFIMA (0,0,0) .
-1/2 < d < 0 ARFIMA (0, d,0) . ( ) . .
d = - 1/2 ARFIMA (0, -1/2, 0) - , , . ω→ 0.
d = 1/2 ARFIMA (0, 1/2, 0) S (ω) = 1 / [2 sin (0,5 ω)] ~ ω-1 ω→ 0. , 1/ f.
, ARFIMA p q . (3.3), d . p q, ARFIMA ( 1, d, 0) ARFIMA (0, d, 1).
, ARFIMA (1, d,0)
(1 - B) (1 B) d Xt = at.
Yt = (1 - B) Xt, , (1 B) d Yt = at. , { t } , ARFIMA (0, d,0). , { t } { Yt }, { t } . { t } , .
{ t } . [11] :
- .
, . , .
ARFIMA (0, d,1)
(1 B) d Xt = (1 - θ B) at,
.
.
{ t }
{ t }
, , .
: ARFIMA (1, d,0) d = 0,2 = 0,366 ARFIMA (0, d,1) d = 0,2 = -0,508 (.3.25).
.3.25.
ARFIMA (1, d,0) ARFIMA (0, d,1)
, .3.25, , ARFIMA (0, d,1) , ARFIMA (1, d,0), , .
ARFIMA(p, d, q), (3.3), (B), θ(B) . , d , θ . , d , θ - .
|
|
Xt d ≠ 0 d I (d). . - 0,5 < d < 0,5 , d < 1 . I (d) , S (0) = 0 d < 0 S (0) → ∞ d > 0. d > 0 S (ω) ~ ω-2 d; d > 0,5 .
[15] ARFIMA (p, d, q) , . , (B) θ(B) ,
) (B) { z: | z |=1}, (3.3)
ψ (z) = (1 z)- d θ(z) / (z).
) (B) ࠠ { z: | z | ≤1}, Xt ().
) (B) ࠠ { z: | z | ≤1}, Xt .
, ( )
(3.37)
ψ 0 = 1; { at } - σ2, , Xt .
(3.37) , {π j } ,
(3.38)
(3.38) , π0 = -1, Xt
(3.39)
, ARFIMA (p, d, q) , ,
= ψ (B) at
ARFIMA (p, d, q) , [14]. (∞) ψ j AR (∞) π j j → ∞
(d) - -.
(3.40)
-
,
, ,
(3.41)
, ARMA
(3.42)
, , (3.41).
ARFIMA (p, d, q), . ARFIMA (p, d, q) .