TGARCH variance

12 vues (au cours des 30 derniers jours)
Besnik
Besnik le 24 Mai 2012
Hi I have estimate the conditional variance of a given financial time series data under the hypothesis that the returns follow a student t distribution with this specification
spec = garchset('P',1,'Q',1,'C',NaN,'Distribution','T','Display','off');
h=par.K + par.ARCH+par.GARCH;
I want this to estimate the Value at Risk. What I wanna know is if the variance estimated with this code is corrected by the degrees of freedom (I have set the degrees of freedom 10).I can't find in any manual how this variance is estimated and if is corrected by the degrees of freedom! Thank you very much.
EDIT [25 May 2012, 13:36 BST - OK] Added code from comments.
T=length(r); WE=1000;
p = 0.01;
VaR = zeros(T,1);
spec = garchset('P',1,'Q',1,'C',NaN,'Distribution','T','Display','off');
for t=WE+1:T
t1 = t-WE; t2 =t-1;
window = r(t1:t2);
[par, errors, LLF, innovations, ht]=garchfit(spec,window);
h=par.K + par.ARCH*window(end)^2+par.GARCH*ht(end)^2;
VaR(t,1)=-sqrt(h)*tinv(p,10);
end
  2 commentaires
Oleg Komarov
Oleg Komarov le 24 Mai 2012
I think you skipped some lines of code, where does 'par' come from?
Besnik
Besnik le 25 Mai 2012
Hi the code is
T=length(r); WE=1000; p = 0.01: VaR = zeros(T,1); spec = garchset('P',1,'Q',1,'C',NaN,'Distribution','T','Display','off'); for t=WE+1:T t1 = t-WE; t2 =t-1; window = r(t1:t2); [par, errors, LLF, innovations, ht]=garchfit(spec,window); h=par.K + par.ARCH*window(end)^2+par.GARCH*ht(end)^2; VaR(t,1)=-sqrt(h)*tinv(p,10); end
with this code I estimate the parameters and calculate the variance under the hypothesis that the returns follow a student t distribution. par is for parameter. What I want to know is if the variance calculated in this way is corrected by the degrees of freedom this is very important for my thesis. Thank you.

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