The bug is very small, run
ma = {0.00001,0.00001}
set initvals ma
catch arma 1 1; pop --nc --opg
ma = {-0.9,-0.9}
set initvals ma
catch arma 1 1; pop --nc --opg
ma = {0,0}
set initvals ma
catch arma 1 1; pop --nc --opg
set initvals auto
catch arma 1 1; pop --nc --opg
Oleh
20 лютого 2018, 23:37:30, від oleg_komashko(a)ukr.net:
Dear all,
An example to reproduce
function void arma11_via_kalman (series y)
/* listing 33.1 with '--hessiaan' dropped */
/* parameter initialization */
scalar phi = 0
scalar theta = 0
scalar sigma = 1
/* state-space model setup */
matrix H = {1; theta}
matrix F = {phi, 0; 1, 0}
matrix Q = {sigma^2, 0; 0, 0}
bundle kb = ksetup(y, H, F, Q)
/* maximum likelihood estimation */
mle logl = ERR ? NA : kb.llt
kb.obsymat[2] = theta
kb.statemat[1,1] = phi
kb.statevar[1,1] = sigma^2
ERR = kfilter(&kb)
params phi theta sigma
end mle
end function
set verbose on
arma11_via_kalman(pop)
arma 1 1; pop --nc --conditional
catch arma 1 1; pop --nc
catch arma 1 1; pop --nc --x-12-arima
Question: why the natives do not use
this trick?
Oleh
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