spatial point processes in aid of rainforest ecology
TRANSCRIPT
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
T u o m a s R a j a l a
U n i v e r s i t y o f J y v s k y l , F i n l a n d
S u p e r v i s o r s : A . P e n t t i n e n , J . I l l i a n
F u n d i n g : C O M A S
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
W h a t i s t h i s t a l k a b o u t :
E x a m p l e o f e c o l o g i c a l q u e s t i o n r e l a t e d t o b i o d i v e r s i t y
I n t r o d u c t i o n t o s p a t i a l p o i n t p r o c e s s e s
M e a s u r i n g d i v e r s i t y i n s p a t i a l c o n t e x t
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 2 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
R a i n f o r e s t d a t a : B a r r o C o l o r a d o I s l a n d , P a n a m a
T h e 5 0 - h e c t a r e p e r m a n e n t t r e e p l o t w a s e s t a b l i s h e d i n 1 9 8 0 i n t h e
t r o p i c a l f o r e s t o f B a r r o C o l o r a d o I s l a n d ( B C I ) i n G a t u n L a k e i n c e n t r a l
P a n a m a . C e n s u s e s h a v e b e e n c a r r i e d o u t i n 1 9 8 1 - 1 9 8 3 , 1 9 8 5 , 1 9 9 0 , 1 9 9 5 ,
2 0 0 0 , a n d 2 0 0 5 . I n e a c h c e n s u s , a l l f r e e - s t a n d i n g w o o d y s t e m s a t l e a s t
1 0 m m d i a m e t e r a t b r e a s t h e i g h t w e r e i d e n t i e d , t a g g e d , a n d m a p p e d .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 3 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
Topography of area
12
0
130
140
150
160
Intensity map of the trees
1000
3000
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 4 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
Q u e s t i o n s o f b i o d i v e r s i t y 1
G l o b a l , c o m m u n i t y l e v e l q u e s t i o n s :
Q 1 S p e c i e s r i c h n e s s : H o w m a n y s p e c i e s ?
S
:= #s p e c i e s
Q 2 S p e c i e s e v e n n e s s : H o w e v e n i s t h e a b u n d a n c e d i s t r i b u t i o n ?
R e l a t i v e a b u n d a n c e s : = 1 , . . . ,
S,
:= n /n .
S e v e r a l i n d i c e s a r e u s e d t o m e a s u r e e v e n n e s s , e . g .
S i m p s o n i n d e x :=
S
= 1 2
.
C e n s u s ' 8 1 - ' 8 3 ' 8 5 ' 9 0 ' 9 5 ' 0 0 ' 0 5
n 2 3 5 2 8 2 2 4 2 0 4 6 2 4 3 9 9 9 2 2 9 0 2 0 2 1 3 7 6 9 2 0 8 3 7 0
S 2 8 5 2 8 7 2 8 8 2 8 1 2 8 0 2 8 2
0 . 0 5 1 0 . 0 5 2 0 . 0 5 2 0 . 0 5 2 0 . 0 5 1 0 . 0 4 9
N o w w e h a v e m o r e d e t a i l e d d a t a s o w e c a n a s k m o r e . . .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 5 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
Q u e s t i o n s o f b i o d i v e r s i t y 2
L o c a l , i n d i v i d u a l l e v e l q u e s t i o n s :
Q 1 I n t e n s i t y a r o u n d i n d i v i d u a l s
H o w d e n s e i s t h e s u r r o u n d i n g a r e a , s i z e o f n e i g h b o u r h o o d ,
a n d
h o w i t a e c t s t h e i n d i v i d u a l ' s s u r v i v a l ?
Q 2 I n t e r s p e c i e s r e l a t i o n s h i p s
D o s p e c i e s d i e r i n t h e i r n e i g h b o u r h o o d s ?
W h a t i s t h e r o l e o f a s p e c i e s i n t h e c o m m u n i t y ?
L e t ' s t r y t o a n s w e r Q 2 .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 6 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
M a t h e m a t i c a l f r a m e w o r k
L o c a l l e v e l q u e s t i o n s r e q u i r e
T r e a t m e n t o f i n d i v i d u a l u n i t s w i t h k n o w n l o c a t i o n s
d e n i t i o n o f ' l o c a l '
p o s s i b i l i t y t o s t a t i s t i c a l l y e s t i m a t e g l o b a l a n d s p e c i e s s p e c i c
f e a t u r e s
s t o c h a s t i c i t y , a s t h e f o r e s t i s h i g h l y c o m p l i c a t e d s y s t e m
S u i t a b l e m a t h e m a t i c a l f r a m e w o r k
1
i s g i v e n b y
S p a t i a l p o i n t p r o c e s s e s
1
e . g . M a t r n ' 6 0 , R i p p l e y ' 7 6 , D i g g l e ' 8 3 , S t o y a n e t a l . ' 9 5 , I l l i a n e t a l . ' 0 8
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 7 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
S p a t i a l p o i n t p r o c e s s e s
S p a t i a l p o i n t p r o c e s s i s i n t h i s c o n t e x t u n d e r s t o o d a s a
r a n d o m , l o c a l l y n i t e s e t X
= {x
i }o f d i s c r e t e p o i n t s i n
Rd
.
D a t a p a t t e r n
xi s a s i n g l e i n s t a n c e X () = x o f s p a t i a l p o i n t
p r o c e s s m o d e l .
T h e i n t e r e s t i s i n t h e d i s t r i b u t i o n a l p r o p e r t i e s o f X : i n t e n s i t y
, s p a t i a l c o r r e l a t i o n o f p o i n t s , h o m o g e n e i t y , i s o t r o p i a , . . .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 8 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
T h e c o m p l e t e s p a t i a l r a n d o m n e s s i s d e s c r i b e d b y t h e P o i s s o n
p r o c e s s : n o i n t e r a c t i o n b e t w e e n p o i n t s .
M o d e l s c a n b e g i v e n t r o u g h a d e n s i t y f
X
w i t h r e s p e c t t o t h e
P o i s s o n p r o c e s s p :
P(X A ) =
A
f
X
(x
)d p (x
)
E x a m p l e : l e f t : P o i s s o n f
X
1 .r i g h t : H a r d c o r e p r o c e s s f
X
1 ( m i n || xi
xj
|| > 0 .0 5 ) .
Poisson
0 1
0
1
Hard core,h=0.05
0 1
0
1
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 9 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
M u l t i t y p e s p a t i a l p o i n t p r o c e s s e s
M u l t i t y p e ( s p a t i a l ) p o i n t p r o c e s s e s a r e s p a t . p o i n t p r o c e s s e s
w i t h a d d i t i o n a l i n f o r m a t i o n o n t h e p o i n t s , M
= {[x
i ;t
(x
i )]}.
T h e t y p e s t ( xi
) {1 ,..., S } c a n r e p r e s e n t t h i n g s l i k e s p e c i e s , c o l o r , s i z e c l a s s , e v e n t ( o n / o ) , r o l e ( f a c t o r y / c o n t a m i n a t i o n ) ,
s t a t e o f g r o w t h , s e x . . .
betacells
ants
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 0 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
T o o l s f o r a n a l y s i n g p o i n t p r o c e s s e s
W h e n a p o i n t p a t t e r n d a t a i s g i v e n s u m m a r y s t a t i s t i c s a r e
c a l c u l a t e d , e . g .
I n t e n s i t y n| W |
K
- f u n c t i o n : K
(r
) = Eo
x X 1 (x B (o , r ) \ {o }).
M u l t i t y p e v e r s i o n s a l s o p o s s i b l e
I n t e n s i t y
n
|W
|
K , = E o ,
x X 1 (
x
B(
o,
r) \ {
o}).
Ants nests
0 2 4 6 8 10 12
0
1
2
3
4
r
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 1 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
B a c k t o t h e j u n g l e
N o w , w r i t e M = {[x
i
; t (xi
)]} f o r a m u l t i t y p e p o i n t p r o c e s s w i t h i n t e r p r e t a t i o n s
x
i
t r e e l o c a t i o n
t(
x
i
) t r e e s p e c i e s
I n t h e s m a l l s a m p l e S = 5 6 , s o r o u g h l y 1 5 0 0 d i e r e n t K - f u n c t i o n s t o c o m p a r e .
H o w a b o u t s u m m i n g u p t h e d i v e r s i t y i n t h e ' n e i g h b o u r h o o d s ' ?
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 2 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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M e a s u r e s o f D i v e r s i t y : S i m p s o n i n d e x
R e c a l l : d e n i t i o n o f S i m p s o n i n d e x
:=S
=1
(
)2 =S
=1
2
S h i m a t a n i & K u b o t a ( 2 0 0 4 ) i n t r o d u c e d t h e S p a t i a l S i m p s o n
i n d e x :
( r ) :=S
=1
2
K ,( r )
K (r ).
S u m m a r i z e s t h e i n f o r m a t i o n i n t h e p a t t e r n : N o d i s t i n c t i o n
b e t w e e n s p e c i e s . . .
0 10 20 30 40 50
0.
00
0.
02
0.
04
0.
06
r
(r)
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 3 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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M e a s u r e s o f D i v e r s i t y : I S A R
W i e g a n d e t . a l l . ( 2 0 0 7 ) : I n d i v i d u a l S p e c i e s - A r e a - R e l a t i o n s h i p
( I S A R ) f u n c t i o n f o r a s p e c i e s :
I ( r ) :=S
=1
P
o,( X B ( o , r ) = )
T h e e x p e c t e d n u m b e r o f s p e c i e s p r e s e n t a r o u n d a t y p i c a l t r e e
o f s p e c i e s
U s e I ( r ) t o s t u d y Q 2 : L o o k f o r s p e c i e s e s w h i c h d e v i a t e s f r o m P o i s s o n p r o c e s s I
0
(r ) .
I f I ( r ) > I
0
( r ), t h e s p e c i e s h a s m o r e d i v e r s i t y a r o u n d i t t h a n
w o u l d b e e x p e c t e d . C a l l t h e s e s p e c i e s d i v e r s i t y a c c u m u l a t o r s .
I f I ( r ) < I
0
( r ), w e c a l l t h e s p e c i e s d i v e r s i t y r e p e l l e r .
T h e s t a t i s t i c a l i n f e r e n c e i s b a s e d o n M o n t e C a r l o - s i m u l a t i o n s .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 4 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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T h e r e s u l t s f o r B C I
D a t a s e t : B C I c e n s u s ' 9 5 , a l l t r e e s w i t h d b h > 1 0 c m . = 2 . 5 %
0 10 20 30 40
0
20
40
60
80
100
r
Percentage
cases
neutral
repelleraccumulator
S u p r i s i n g a m o u n t o f r e p e l l e r s .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 5 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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C o m p a r i n g I S A R ' s
A n o t h e r r a i n f o r e s t p l o t : 5 0 h a p l o t P a s o h , M a l a y s i a . M o r e t h a n
8 0 0 s p e c i e s , o v e r 0 . 3 m i l i n d i v i d u a l s .
F i g u r e d e p i c t s I S A R f o r s u b s e t o f i n d i v i d u a l s w i t h
d b h > 1 0 c m f o r s p e c i e s w i t h n > 7 0 .
0 10 20 30 40 50
0
2
0
40
60
80
r
I(r)
BCI
Pasoh
0 10 20 30 40 50
0.0
0
0.1
0
0.2
0
0.3
0
r
I(r)/S
BCI
Pasoh
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 6 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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B a c k t o m a t h : t h e n e i g h b o u r h o o d s
T h e n e i g h b o u r h o o d d e n i t i o n u s e d w a s
y n e ( x ) y B ( x , r )
f o r a x e d r > 0 .
W h a t i f w e w a n t t o d e n e t h e n e i g h b o u r h o o d r e l a t i o n
d i e r e n t l y ?
T h e t h e o r y f o r s t u d y i n g n e i g h b o u r h o o d r e l a t i o n s h i p s : G r a p h
t h e o r y g e n e r a l f r a m e w o r k f o r n e i g h b o u r h o o d s
G r a p h i s d e n e d a s a p a i r G (V ) = ( V , E ) w h e r e V i s an o n - e m p t y s e t c a l l e d v e r t e x s e t , a n d E {x y :, x , y V } t h ee d g e s e t . ( w r i t e x y E x y ) .
D e n i t i o n o f
n e i g h b o u r h o o d o f a p o i n t x V :
n e ( x ) := {y V : x y }.
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 7 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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T h e t y p e o f i n f o r m a t i o n o f X i n G (X ) i s c o v e r n e d b y t h e c o n s t r u c t i o n r u l e o f E . C o m m o n e x a m p l e s :
G e o m e t r i c g r a p h f o r R > 0 :
x y d ( x , y ) R
f o r s o m e m e t r i c d (, ) .
k - n e a r e s t n e i g h b o u r s g r a p h , k > 0 : i f
d
k
( x ) := i n f {r > 0 : N ( b ( x , r )\{x }) = k }
i s t h e d i s t a n c e t o t h e k t h n e i g h b o u r i n g
p o i n t o f x , t h e n
x y d ( x , y ) dk
( x ).
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 8 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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R a n d o m g r a p h s
G r a p h t h e o r e t i c a l f e a t u r e s r e e c t t h e s t r u c t u r e o f t h e p o i n t p r o c e s s .
E x a m p l e :
M e a n c o n n e c t i o n s p e r p o i n t o r m e a n d e g r e e
d e g :=E
o
x N
1( o x ).
I f n e i g h b o u r h o o d i s g i v e n b y g e o m e t r i c g r a p h w i t h p a r a m e t e r
r > 0 ,d e g = K (r ),
i . e . t h e i n f o r m a t i o n o f R i p l e y ' s K - f u n c t i o n i s a n e x a m p l e o f
g r a p h s u m m a r y .
S a m e c a n b e d o n e t o a n y f u n c t i o n o f s o m e n e i g h b o u r h o o d ,
e . g . t h e I S A R f u n c t i o n :
I ( G (X )) =S
=1
P
o
(X n e (o ) = )
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 1 9 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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B C I v s . P a s o h : k
- n e a r e s t n e i g h b o u r s
U p p e r : M e t r i c n e i g h b o u r h o o d , g e o m e t r i c g r a p h
L o w e r : T o p o l o g i c a l n e i g h b o u r h o o d , k - n e a r e s t n e i g h b o u r s g r a p h .
0 10 20 30 40 50
0
20
40
60
80
r
I(r)
BCI
Pasoh
0 10 20 30 40 50
0.0
0
0.1
0
0.2
0
0.3
0
r
I(r)/S
BCI
Pasoh
0 20 40 60 80 100
0
10
20
30
40
50
knn
I(r)
BCI
Pasoh
0 20 40 60 80 100
0.0
0
0.0
4
0.0
8
0.1
2
knn
I(r)/S
BCI
Pasoh
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 2 0 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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F r o m 1 D t o 2 D : G e n e r a l c o n s e p t o f D i v e r s i t y
Equality Segregation RegularityClusteringDominance Mingling
T w o a s p e c t s o f c l a s s i c a l d i v e r s i t y : R i c h n e s s a n d e v e n n e s s
T h e t w o a s p e c t s o f s p a t i a l d i v e r s i t y : E x p o s u r e a n d s c a t t e r i n g
1
P r o b l e m : E x p o s u r e a n d s c a t t e r i n g a r e n o t i n d e p e n d e n t
T o p o l o g i c a l n e i g h b o u r h o o d s m i g h t h e l p s e p a r a t e t h e t w o
a s p e c t s
1
P i e l o u ' 7 7 , A g u i r r e e t a l . ' 0 3 , S h i m a t a n i e t a l . ' 0 4 .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 2 1 / 2 4
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S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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C o n c l u s i o n s
R a i n f o r e s t s b i o d i v e r s i t y : S h o w n m e t h o d s a l l o w s u s t o e . g . t e s t
v a l i d i t y o f d i e r e n t t h e o r i e s ( n e u t r a l v s . n i c h e )
G e n e r a l c o n s e p t o f d i v e r s i t y , a l s o i n 2 D ? ( S o s i o l o g y , m a t e r i a l
s c i e n c e s , c h e m i s t r y , g e n o l o g y . . . )
N e i g h b o u r h o o d s : m a t h e m a t i c a l f r a m e w o r k ( G r a p h s )
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 2 3 / 2 4
S p a t i a l p o i n t p r o c e s s e s i n a i d o f r a i n f o r e s t e c o l o g y
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L i t e r a t u r e
A r t i c l e s :
H u b b e l l , C o n d i t , F o s t e r : B a r r o C o l o r a d o f o r e s t c e n s u s p l o t d a t a .
U R I : h t t p : / / c t f s . s i . e d u / d a t a s e t s / b c i /
2 0 0 5
S h i m a t a n i , K u b o t a : " Q u a n t i t a t i v e a s s e s s m e n t o f m u l t i s p e c i e s
s p a t i a l p a t t e r n w i t h h i g h s p e c i e s d i v e r s i t y " , E c o l o g i c a l r e s e a r c h
, v . 1 9 ,
2 0 0 4
W i e g a n d , G u n a t i l l e k e , G u n a t i l l e k e , H u t h : H o w i n d i v i d u a l s p e c i e s
s t r u c t u r e d i v e r s i t y i n t r o p i c a l f o r e s t s , P N A S , n o v . 1 6 2 0 0 7
B o o k s :
B u r s l e m , P i n a r d , H a r t l e y :
B i o t i c i n t e r a c t i o n s i n t h e t r o p i c s ,
C a m b r i d g e 2 0 0 5 .
I l l i a n , P e n t t i n e n , S t o y a n , S t o y a n :
S t a t i s t i c a l a n a l y s i s a n d m o d e l l i n g
o f s p a t i a l p o i n t p a t t e r n s , W i l e y 2 0 0 8 .
M a r c h e t t e :
R a n d o m g r a p h s f o r s t a t i s t i c a l p a t t e r n r e c o g n i t i o n , W i l e y
2 0 0 4 .
T u o m a s R a j a l a , U n i v e r s i t y o f J y v s k y l , F i n l a n d 2 4 / 2 4