Hi,
Using a model without a constant a got:
Model 2: ARMA estimates using the 30 observations 1971-2000
Dependent variable: sales
VARIABLE COEFFICIENT STDERROR T STAT P-VALUE
car(-1) 0.460111 0.928532 0.496 0.62410
e(-1) -0.673785 0.773696 -0.871 0.39123
The model has no constant term.
F is calculated as in Sect. 4.4 of Ramanathan's Introductory Econometrics.
R-squared is the square of the correlation between the observed and fitted
values of the dependent variable.
----- Original Message -----
From: "John Paravantis" <paravantis(a)otenet.gr>
To: <gretl-users(a)ricardo.ecn.wfu.edu>
Sent: Monday, January 30, 2006 10:10 PM
Subject: [Gretl-users] ARMA bug?
Methinks I found a bug in ARMA.
Copy/paste the following data into a gretl column (possibly pasting into
Word and ALT-copying and pasting the column into Excel):
0.019
0.046
-0.16
0.328
0.077
0.408
-0.08
-0.166
-0.596
0.344
0.008
0.053
0.026
0.383
-0.196
-0.23
0.012
0.249
0.276
-0.881
0.089
0.742
-0.164
0.109
-0.006
0.2
0.115
0.718
0.138
-0.299
-0.009
(They are 2nd differences of car ownership per 100 people in Greece, from
1970 to 2000 appr.)
Then try to run an ARMA(1,1): you get a dialog that "The convergence
criterion is not met". Unfortunately, it is possible to fiddle with the
convergence criterios (# of iterations) on the ARMA dialog box!
Here comes worse. Try to estimate an ARMA(0,1) WITHOUT THE CONSTANT: you
get an "out of memory error"!
Incidentally, these estimate ok in Statgraphics 5.1.
BTW thanks to all for your kind responses to my graph querry:
- Peter (of Colorado), many thanks for your tip -- I would rather not go
through the PNG format because unlike vector graphics it deteriorates when
zoomed and is usually not accepted by research journals.
- Jean, your appropriate reference to Gnumeric made me delve deeper into
Excel 2003 (yuck!) only to find out that the reason I do not get the
format confirmation dialog anymore is that Excel 2003 has now a separate
menu (Data>Import External Data...) that imports other formats! Using that
menu worked fine!
Warmest regards to all,
John
University of Piraues
Greece
PS I am mailing a separate gretl file with the above data to Allin (I
cannot attach files to the user forum address, can I?)
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