Hamzi - Eurandom

Parameter Estimation for SDEs
• Consider the scalar-valued SDE
• Equation Lρ∞(x) = 0 reduces to
dXt = f(Xt) dt + g(Xt) dWt .
f(x)ρ∞(x) = 1
2 (g(x)2 ρ∞(x)) ′ .
The methodology described before yields an estimator ˆρ∞ of ρ∞, but this
is obviously not sufficient to estimate both unknown functions f and g
directly using the above relation. If we, however, have knowledge of either
one, then a natural nonparametric estimator for the other one is given via
or
ˆf(x) = g(x)g ′ (x) + g(x)2 ˆρ ′ ∞(x)
2ˆρ∞(x)
ˆg(x) 2 = 2
ˆρ∞(x)
∫ x
0
f(u)ˆρ∞(u) du ,
. . . . . .
Boumediene Hamzi (Imperial College) On Control and RDS in RKHS June 4th, 2012 50 / 55