msmna93 - 9 days ago 4x
R Question

Loop for ARMA model estimation

Suppose that I have the following "for" loop in R.

``````USDlogreturns=diff(log(prices))

for(i in 0:5){
for(j in 0:5){
fit <- arima(USDlogreturns, order=c(i,0,j), include.mean=TRUE)
}
}
``````

How do you tell R to substitute a NA matrix with the coefficients of all the estimated models?

You will need a matrix `M` with dimensions 36 times 13. Then use

``````M=matrix(NA,36,13)
k=0 # current row being filled in
for(i in 0:5){
for(j in 0:5){
k=k+1
fit <- arima(USDlogreturns, order=c(i,0,j), include.mean=TRUE)
if(i>0) M[k,c(1:   i) ]=fit\$coef[c(   1 :   i )] # AR coefficients in the 2nd-6th columns
if(j>0) M[k,c(8:(7+j))]=fit\$coef[c((i+1):(i+j))] # MA coefficients in the 8th-12th columns
M[k,      13  ]=tail(fit\$coef,1)         # "intercept" (actually, mean) in the 13th column
}
}
``````

The columns 2 to 6 will contain AR coefficients.
The columns 8 to 12 will contain MA coefficients.
The 13th column will contain the "intercepts" (actually, the means, as the terminology in the `arima` function is misleading).

Source (Stackoverflow)