Question rmgarch package
There could be any number of reasons this is happening, but I just can't tell from the information you've provided. I suggest you try to eliminate some possibilities as a first pass: 1. Use: startMethod = "sample" (in gogarchsim) 2. You're providing your own ICA decomposition matrices in the spec. Try using the default estimation first (and set n.comp=4) without providing your own matrices. 3. Try without dimensionality reduction. 4. The convolution method has additional fine tuning parameters. You may need to adjust those (fft.step, fft.by etc). 5. For comparison, try a Cornish-Fisher expansion as explained here: http://unstarched.net/r-examples/rmgarch/var-and-approximate-var-in-the-go-garch-nig-model/ Regards, Alexios
On 25/06/2015 21:27, daniel melendez via R-SIG-Finance wrote:
Hello All - I am trying to complete a simulation based off of given information from a gogarchfit object but I seem to be obtaining really low VaR numbers. Can anyone help explain this? Also I saw on a previous post from the r-sig-finance mailing list that the standardized residuals can be obtain by taking the square root of the covariance matrix, however, I seem to be getting rather large numbers. Can anyone help explain this too? Any help would greatly appreciated. The code snippets are below: # specs for GO-GARCH model
#----------------------------------------------------------------------------
spec = gogarchspec(mean.model = list(model = 'constant'),
variance.model = list(model = 'eGARCH',
garchOrder = c(1, 1), variance.targeting = TRUE),
distribution = 'manig', ica = 'fastica',
ica.fix = list(A = est_mixing_matrix, K = whitening_matrix,
W = est_unmixing_matrix, U = est_rotation_matrix,
Kinv = dewhitening_matrix, Y = est_indep_components_matrix)) # GO-GARCH Fit
#----------------------------------------------------------------------------
cl <- makePSOCKcluster(3)
mod2 = gogarchfit(spec = spec, data = garchSeries, gfun = 'tanh', cluster = cl,
solver = "hybrid", firstEig = 1, lastEig = 4,
solver.control = list(trace = 1),
maxiter1 = 40000, epsilon = 1e-08, rseed = 972,
fit.control = list(stationarity = 1))
stopCluster(cl) # Simulation Generation
# --------------------------------------------------------------------------------
cl <- makePSOCKcluster(3)
sim1 <- gogarchsim(mod2, n.sim = 50, n.start = 0,
m.sim = 5000,
rseed = 214, cluster = cl)
stopCluster(cl) cf = convolution(sim1, weights = matrix(rep(1/10, 10), ncol = 10, nrow = 50))
VaR = matrix(NA, ncol = 2, nrow = 50)
colnames(VaR) = c('qfft[0.9999]', 'qfft[0.0001]')
for (i in 1:50){
qfx = qfft(cf, index = i)
VaR[i, 1] = qfx(0.9999)
VaR[i, 2] = qfx(0.0001)
}
matplot(VaR, type = 'l') #----------------------------------------------------------------------# Calculate the standardized residuals for the model
# ---------------------------------------------------------------------
residualsModel <- residuals(mod2)
cov.sq <- rcov(mod2)
sq.cov <- array(NA, dim = c(dim(cov.sq)[1],
dim(cov.sq)[2],
dim(cov.sq)[3]))
sq.cov.mat <- function (x){
tmp = svd(x)
sqrtx = tmp$u %*% sqrt(diag(tmp$d)) %*% t(tmp$u)
return(sqrtx)
}
for(i in 1:dim(cov.sq)[3]){
sq.cov[,,i] <- solve(sq.cov.mat(cov.sq[,,i]))
}
stand.resid <- matrix(NA, ncol = ncol(residualsModel), nrow = nrow(residualsModel))
for(i in 1:dim(sq.cov)[3]){
stand.resid[i,] <- t(sq.cov[,,i] %*% as.numeric(residualsModel[i,]))
} Regards
Daniel Melendez
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