ͱ Pn i=1 ci = 0 Λຬͨ͢ҙͷෳૉ c1; : : : ; cn 2 C ʹ͍ͭͯɼ n X i;j=1 ci — cjk (xi; xj) = n X i;j=1 ci — cja = n X j=1 — cj 0 @ n X i=1 cia 1 A = 0 » 0 ΑΓɼk ෛఆΧʔωϧɽ 2 › (3) ҙͷؔ f ͱ Pn i=1 ci = 0 Λຬͨ͢ҙͷෳૉ c1; : : : ; cn 2 C ʹର͠ɼ n X i;j=1 ci — cj (xi; xj) = n X i;j=1 ci — cj (f(xi) + f(xj)) = n X j=1 — cj 0 @ n X i=1 cif(xi) 1 A + n X i=1 ci 0 @ n X j=1 — cjf(xj) 1 A = 0 » 0 ΑΓɼ ෛఆΧʔωϧɽ 2 5
1; : : : ; n) ΛҙʹͱΓɼc0 := ` Pn i=1 ci ͱ͢Εɼ ͷෛఆੑ͔Βҙͷ x0; x1; : : : ; xn 2 X ʹରͯ͠ɼ n X i=0;j=0 ci— cj (xi; xj) » 0 ͕Γཱͭɽ্ࣜͷࠨล i = 0; j = 0 ͷ߹Λ֎ʹग़ͤɿ n X i=0;j=0 ci— cj (xi; xj) = n X i=0 n X j=0 ci— cj (xi; xj) = n X i;j=1 ci— cj (xi; xj) + c0 n X i=1 ci (xi; x0) + c0 n X j=1 cj (x0; xj) + jc0j2 (x0; x0) = n X i;j=1 cicj (xi; xj) ` n X i;j=1 cicj (xi; x0) ` n X i;j=1 cicj (x0; xj) + n X i;j=1 cicj (x0; x0) = ` n X i;j=1 cicj’ (xi; xj) ͱͳͬͯɼPn i;j=1 cicj’ (xi; xj) – 0 ͔Β ’ ਖ਼ఆͰ͋Δɽ 2 9
p `1!Txd˜ (!) ͱද͞ΕΔͱ͢Δɽ e p `1!T(x`y) = e p `1!Txe` p `1!Ty = e p `1!Txe p `1!Ty Ͱ͋Δ͔Β (७ڏ z ʹରͯ͠ `z = z Ͱ͋Δ͜ͱͱ exp `z´ = exp (z) Λͬͨ)ɼҎԼͷ Χʔωϧɿ K (x; y) := ffi (x ` y) = Z e p `1!Txe p `1!Tyd˜ (!) ͷඃੵ໋ؔ 2.5(2) ͔Βਖ਼ఆΧʔωϧͰ͋ΔɽΑͬͯɼͦͷੵͱͯ͠ಘ ΒΕΔ K ਖ਼ఆΧʔωϧͰ͋Γɼffi ਖ਼Ͱ͋Δɽ 2 › ඞཁੑ: লུɽ Bochner ͷఆཧɼҙͷਖ਼࿈ଓ͕ؔ fe p `1!Tx j ! 2 Rng ͷඇෛ݁߹ͱ͠ ͯද͞ΕΔ͜ͱΛओு͍ͯ͠Δɽ 17
͕ҎԼͷΑ͏ͳܗΛͭͱԾఆ͢Δɽ K (x; y) = Z e p `1!T(x`y)ȷ (!) d! ͨͩ͠ɼȷ ࿈ଓͰɼȷ (!) > 0; R ȷ (!) d! < 1ɽ ͜ͷ࣌ɼK Λ࠶ੜ֩ͱ͢Δ RKHSɿHK HK = ( f 2 L2 (R; dx) j Z ˛ ˛ ^ f (!)˛ ˛ 2 ȷ (!) d! < 1 ) hf; gi = Z ^ f (!) ^ g (!) ȷ (!) d! ͨͩ͠ɼ ^ f f ͷ Fourier มɿ ^ f (!) = 1 (2ı)m R f (x) e` p `1!Txd! 18
—) ʹ͓͍ͯ K (x; y) ҎԼͷΑ͏ʹల։Ͱ͖Δɽ ఆཧ 6.13 Hermite తͳੵ֩ K ʹର͢Δੵ࡞༻ૉ TK ͷඇθϩݻ༗ –i ͱ୯Ґݻ༗ϕΫτϧ ffii Λઌड़ͷΑ͏ʹ͢Δɽ͜ͷ࣌ɼL2 (˙ ˆ ˙; — ˆ —) ʹ͓͍ͯɼ K (x; y) = 1 X i=1 –iffii (x) ffii (y) ͷల։͕Γཱͭɽ Fubini ͷఆཧ ˙ Λଌۭؒͱ͠ɼf (x; y) ͕Մଌ͔ͭՄੵͰ͋ΔͳΒɼҎԼཱ͕͢Δɽ Z ˙ Z ˙ f (x; y) dy ! dx = Z ˙ Z ˙ f (x; y) dx ! dy = Z ˙ˆ˙ f (x; y) d (x; y) 29
ʹରͯ͠ N ! 1 Ͱ 0 ʹऩ ଋɽ͔ͭɼ ‚ ‚ ‚ ‚ ‚ ‚ K (x; ´) ` N X i=1 –iffii (x) ffii ‚ ‚ ‚ ‚ ‚ ‚ 2 L2(˙;—) = * K (x; ´) ` N X i=1 –iffii (x) ffii; K (x; ´) ` N X i=1 –iffii (x) ffii + L2(˙;—) = Z jK (x; y)j2 d— (y) ` N X i=1 –2 i jffii (x)j2 » Z jK (x; y)j2 d— (y) ͱ N ʹΑΒͳ͍ 2 ՄੵؔͰ্͔Β͑Δ͜ͱ͕Ͱ͖ɼ༏ऩଋఆཧʹΑͬͯࣜ (6.5) N ! 1 Ͱ 0 ʹऩଋ͢Δɽ 2 31
H ʹରͯ͠ H ্ͷઢܗ൚ؔ ffiF : H ! R ΛҎԼͷΑ͏ʹఆΊΔɿ ffiF (f) := E[hf; F i] Ϧʔεͷදݱఆཧ͔Βɼҙͷ f 2 H ʹରͯ͠ɼ͋Δ mF 2 H ͕ଘࡏ͠ɼ hf; mF i = ffiF (f) ͕ΓཱͭɽΑͬͯ ffiF (f) = E[hf; F i] = hf; mF i (8.1) Λ͑Δɽ͜ͷ mF Λ֬ม F ͷฏۉͱݺͼɼE[F ] Ͱද͢ɽ͜ͷ࣌ɼ E[hf; F i] = hf; mF i = hf; E[F ]i ͱͳΓɼฏۉͱੵͷૢ࡞ަՄೳͰ͋Δɽ 45
X)] < 1 ΛԾఆ͢Δɽ ಛࣸ૾ ˘ (x) = k (´; x) ʹରͯ͠ɼ࠶ੜੑ͔Β k˘ (X)k2 = hk (´; X) ; k (´; X)i = hkX ; kX i = kX (X) = k (X; X) ͕Γཱͭ͜ͱʹҙ͢ΕɼE k˘ (X)k < 1 ͱͳΓɼલ߲ͷԾఆΛຬͨ͠ɼ֬ม ˘ (X) ͷฏۉ mk X ͕ଘࡏ͢Δɽ͜ͷ࣌ɼmk X ΛɼX ͷ Hk ʹ͓͚ΔฏۉɼͱݺͿɽࣜ (8.1) ͓Αͼ࠶ੜੑ͔Βɼҙͷf 2 H ʹରͯ͠ ˙f; mk X ¸ = E[hf; ˘ (X)i] = E[hf; K (X; ´)i] = E[f (X)] (8.2) ͱͳΓɼҙͷ f ʹରͯ͠ظ E[f (X)] ͕ f ͱ mk X ͷੵͰද͞ΕΔɽ ฏۉ mk X ͷཅͳදࣔΛٻΊΔɽmk X 2 H ͔Βɼҙͷ y 2 X ʹ͍ͭͯɼ࠶ੜੑΛ༻͍ Δͱ mk X (y) = ˙mk X ; k (´; y)¸ = hE (˘ (X)) ; k (´; y)i = E hk (´; X) ; k (´; y)i = E[k (X; y)] (8.8) ͱͳͬͯɼฏۉ mk X Χʔωϧؔͷظͱͯ͠༩͑ΒΕΔɽ 46