Displaying 20 results from an estimated 20000 matches similar to: "Define ARMA model"
2009 Apr 29
1
arma model with garch errors
Dear R experts,
I am trying to estimate an ARMA 2,2 model with garch errors.
I used the following code on R 2.9.
#library
library(fGarch)
#data
data1<-ts(read.table("C:/Users/falcon/Desktop/Time
Series/exports/goods1.csv"), start=c(1992,1), frequency=12)
head(data1)
#garch
garchFit(formula.mean= ~arma(2,2),formula.var=~garch(1,1), data=data1)
but get this error:
>
2013 Feb 17
0
forecast ARMA(1,1)/GARCH(1,1) using fGarch library
Hi, i am working in the forecast   of the daily  price crude .
The last prices of this data are the following:
 100.60 101.47 100.20 100.06  98.68 101.28 101.05 102.13 101.70  98.27
  101.00 100.50 100.03 102.23 102.68 103.32 102.67 102.23 102.14 101.25
  101.11  99.90  98.53  96.76  96.12  96.54  96.30  95.92  95.92  93.45
  93.71  96.42  93.99  93.76  95.24  95.63  95.95  95.83  95.65 
2006 Nov 07
1
Comparison between GARCH and ARMA
Dear all R user,
Please forgive me if my problem is too simple.
Actually my problem is basically Statistical rather
directly R related. Suppose I have return series ret
with mean zero. And I want to fit a Garch(1,1)      
on this.
my       is r[t] = h[i]*z[t]
            h[t] = w + alpha*r[t-1]^2 + beta*h[t-1]
I want to estimate the three parameters here;
the R syntax is as follows:
#
2007 Oct 22
1
Newbie help: Data in an arma fit
I'd like to fit an ARMA(1,1) model to some data (Federal Reserve Bank
interest rates) that looks like:
...
30JUN2006, 5.05
03JUL2006, 5.25
04JUL2006, N                  <---- here!
05JUL2006, 5.25
...
One problem is that holidays have that "N" for their data.  As a test, I
tried fitting ARMA(1,1) with and without the holidays deleted.  In other
words, I fit the above data
2004 Oct 25
1
output processing / ARMA order identification
Dear R users,
I need to fit an ARMA model. As far as I've seen, EACF (extended ACF)
is not available in R. 
1. Let's say I fit a series of ARMA models in a loop. Given the
code/output included below, how do I pull 'Model' and 'Fit' (AIC)
from each summary() so that I can combine them into an array/data
frame to be sorted by AIC?
2. Apart from EACF, are you aware perhaps
2013 Apr 08
0
Maximum likelihood estimation of ARMA(1,1)-GARCH(1,1)
Hello
Following some standard textbooks on ARMA(1,1)-GARCH(1,1) (e.g. Ruey
Tsay's Analysis of Financial Time Series), I try to write an R program
to estimate the key parameters of an ARMA(1,1)-GARCH(1,1) model for
Intel's stock returns. For some random reason, I cannot decipher what
is wrong with my R program. The R package fGarch already gives me the
answer, but my customized function
2005 Jun 14
1
using forecast() in dse2 with an ARMA model having a trend component
(My apologies if this is a repeated posting.  I couldn't find any trace
of my previous attempt in the archive.)  
I'm having trouble with forecast() in the dse2 package.  It works fine
for me on a model without a trend, but gives me NaN output for the
forecast values when using a model with a trend.  An example:
# Set inputs and outputs for the ARMA model fit and test periods
2011 Aug 30
2
ARMA show different result between eview and R
When I do ARMA(2,2) using one lag of LCPIH data
This is eview result
>
> *Dependent Variable: DLCPIH
> **Method: Least Squares
> **Date: 08/12/11   Time: 12:44
> **Sample (adjusted): 1970Q2 2010Q2
> **Included observations: 161 after adjustments
> **Convergence achieved after 14 iterations
> **MA Backcast: 1969Q4 1970Q1
> **
> **Variable    Coefficient    Std.
2012 Aug 03
1
AR vs ARMA model
Hi I am trying to fit a time series data.It gives a AR(2) model using the ar
function and ARMA(1,1) model using autoarmafit function in timsac
package.How do I know which is the correct underlying model? pls help 
--
View this message in context: http://r.789695.n4.nabble.com/AR-vs-ARMA-model-tp4639015.html
Sent from the R help mailing list archive at Nabble.com.
2013 May 02
1
warnings in ARMA with other regressor variables
Hi all,
I want to fit the following model to my data:
Y_t= a+bY_(t-1)+cY_(t-2) + Z_t +Z_(t-1) + Z_(t-2) + X_t + M_t
i.e. it is an ARMA(2,2) with some additional regressors X and M.
[Z_t's are the white noise variables]
So, I run the following code:
for (i in 1:rep)  {            index=sample(4,15,replace=T)
 final<-do.call(rbind,lapply(index,function(i)
2003 Nov 24
0
link between arima and arma fit
Hi dear sirs,
I am wondering why the fit of the time serie x with an arima and the fit of
diff(x) with an arma (same coeff p & d) differ one from another
here are the output of R:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> modelarma<-arma(diff(x),c(7,5))
> modelarma
Call:
arma(x = diff(x), order = c(7, 5))
Coefficient(s):
ar1 ar2 ar3 ar4 ar5 ar6 ar7 ma1 ma2 
0.06078
2008 Aug 20
2
arma: what is the meaning of Pr(>|t|)?
In the summary of the output of arma, there's a number Pr(>|t|), however, I 
don't know what is its meaning - at least, it doesn't _seem_ to be a 
Student's t distribution.
Reproducible test case:
  x <- c(0.5, sin(1:9))
  reg <- arma(x, c(1,0))
  summary(reg)
<output>
Call:
arma(x = x, order = c(1, 0))
Model:
ARMA(1,0)
Residuals:
    Min      1Q  Median      3Q 
2008 Mar 21
1
tseries(arma) vs. stats(arima)
Hello,
The "arma"  function in the "tseries"  package allows estimation of models
with specific "ar" and  "ma" lags  with its "lag" argument. 
For example:  y[t] = a[0] + a[1]y[t-3] +b[1]e[t-2] + e[t]  can be estimated
with the following specification :   arma(y, lag=list(ar=3,ma=2)).
Is this possible with the "arima" function in the
2004 Jul 25
1
Multivariate ARMA Model
Hi R-Community,
so far I dealt with univariate processes and used the function "arima" to
estimate an ARMA(1,1)-model. For multivariate processes there are the
functions "estVARXar" and "estVARXls" from package "DSE". But how can I
estimate an VARMA(1,1)-model, or even better determine the orders and
estimate the parameters?
Much thanks in advance,
Hagen
1999 Nov 14
1
bug in arma.sim (PR#322)
Dear Sir,
I think I found a bug in the function arma.sim, which is defined in
the help page of the function filter:
arma.sim <- function(n, ar = NULL, ma = NULL, sigma = 1.0)
{
    x <- ts(rnorm(n+100, 0, sigma^2), start = -99)
    if(length(ma)) x <- filter(x, ma, sides=1)
    if(length(ar)) x <- filter(x, ar, method="recursive")
    as.ts(x[-(1:100)])
}
I am using R
2004 Feb 12
0
How to predict ARMA models?
Hi all,
 
I am fitting an ARMA(1,(1,4)) model.
 
 y(t) = a*y(t-1) + e(t) + b1*e(t-1) + b4*e(t-4)
 
> arma1.14 <- arma(series, lag=list(ar=1, ma=c(1,4)), 
+  include.intercept = F, qr.tol = 1e-07) 
 
works fine:
 
  Coefficient(s):
       ar1     ma1     ma4  
     0.872  -0.445   0.331 
     
I want to forecast 50 periods.
I could not find a 'predict' function for ARMA models.
 
I
2009 Oct 13
0
How to specify an ARMA(1, [1,4]) model? Solved
On Tue, Oct 13, 2009 at 5:06 PM, Rolf Turner <r.turner@auckland.ac.nz>wrote:
>
> Not clear to me what the OP really wants.  Perhaps the seasonal
> model is what's required; perhaps an arima(1,0,4) model with
> theta_2 and theta_3 constrained to be 0.  The latter can be
> achieved with
>
>        arima(x,order=c(1,0,4),fixed=c(NA,NA,0,0,NA,NA))
>
> Or perhaps
2006 Aug 14
1
ARMA(1,1) for panel data
Dear List,
I am new to TS-Modeling in R. I would like to fit an ARMA(1,1) model
for a balanced panel, running Y on a full set of unit and year dummies
using an arma(1,1) for the disturbance:
y_it=unit.dummies+yeardummies+e_it
where: e_it=d*e_it-1+u_it+q*u_it-1
How can I fit this model in R? arma() does not seem to take covariates
(or I don't understand how to specify the function so that
2009 Jun 19
1
using garchFit() to fit ARMA+GARCH model with exogeneous variables
Hello -
 
Here's what I'm trying to do. I want to fit a time series y with
ARMA(1,1) + GARCH(1,1), there are also an exogeneous variable x which I
wish to include, so the whole equation looks like:
 
y_t - \phi y_{t-1} = \sigma_t \epsilon_t + \theta \sigma_{t-1}
\epsilon_{t-1} + c x_t       where \epsilon_t are i.i.d. random
variables
 
\sigma_t^2 = omega + \alpha \sigma_{t-1}^2 + \beta
2013 May 02
2
ARMA with other regressor variables
Hi,
I want to fit the following model to my data:
Y_t= a+bY_(t-1)+cY_(t-2) + Z_t +Z_(t-1) + Z_(t-2) + X_t + M_t
i.e. it is an ARMA(2,2) with some additional regressors X and M.
[Z_t's are the white noise variables]
How do I find the estimates of the coefficients  in R?
And also I would like to know  what technique  R employs to find the
estimates?
Any help is appreciated.
Thanks,