gravity model of trade, negative coefficient of GDP
by Damian Pawlak
Hey there,
I’m now writing a paper about trade relations by means of the gravity model of trade.
In my model I decided to include the fixed country-pair effects. However, after having input those country-pair effects, the coefficient of the GDP of importer is negative, whilst the theory itself says increase of any partner’s GDP (exporter or importer) shall have a positive influence on the trade volume.
If i exclude the fixed effects, the coefficients are positive as expected.
Could anyone give me an explanation to that?
Best regards
Damian
11 years
ARMA with additional regressors - The symbol 'b0' is undefined
by Daniel Bencik
Dear forum,
when estimating an ARMA(x,y) model on my dataset, I receive a "The symbol 'b0' is undefined" error as soon as x > 0, regardless of y, and I have nothing like b0 in my dataset. I tried googling, to no avail. What could be the problem?
Best regards,
Daniel
11 years
ADF TEST CASE 3
by Mark Scerri
HI,
I am rather new to time series analysis. I am trying to perform a unit root
test. I have been advised to perform the test on three cases.
Case 1: no constant term or time trend; True process is a random walk.
Case 2: constant term but no time trend: true process is a random walk.
Case 3: constant term but no time trend; true process is a random walk with
drift.
In Gretl, Case 1 is equivalent to performing the test with the "test
without constant" checked.
Case 2 is equivalent to performing the test with the "with constant"
checked.
For Case 3 I was told to perform case 2 followed by OLS. I am not sure if
this means checking also "show regression results" and if yes how do I
proceed then? If this is not the case what should I do(in simple terms)
after the Case 2 test to get the output of Case 3.
Many thanks
M
11 years
Re : function "ranking"
by Alecos Papadopoulos
I run Gretl 1.10.0cvs build date: 05 Feb 2015 for Windows 64.
I need to use the function "ranking" on column vectors of numbers where
there will always be only two equal numbers, with all others distinct.
The one of the two equal numbers comes from a different calculation
path. The calculation of all these numbers involves natural logarithms.
The problem is that in order for the "ranking" function to recognize
the equality, and provide half-integer ranks as programmed, the two
numbers must be identical to whatever precision they are stored in Gretl.
In practice these two numbers are not totally identical. For example I
obtain
2.8841797876482436
and
2.8841797876482445
But the difference is an artifact of calculation -the two magnitudes
that are represented by these numbers are identical. The difference is
immaterial for all practical purposes -but the function "ranking",
performing as it is supposed to perform, gives rank 12 to the first and
13 for the second. But what I "should" get (so as to be consistent with
the theoretical quantities) is 12.5 and 12.5 . Moreover, it is not known
a priori which of the two will be slightly above or below the other.
A roundabout way to deal with the problem does exist: multiply by some
power of 10 representing desired precision in number of decimals, then
truncate using the function "int", then apply "ranking".
I was just wondering whether it would be worth the programming trouble
to enhance directly the "ranking" function so as to "look" only as deep
as a user-specified number of decimals.
The same added functionality could be given to the function "round",
which currently only rounds to the nearest integer.
It could be a useful feature of Gretl in general, since it would give
the user the ability to specify what constitutes "equal" for his
specific situation, without the need to use the roundabout trick
described above.
--
Alecos Papadopoulos
Athens University of Economics and Business, Greece
Department of Economics
cell:+30-6945-378680
fax: +30-210-8259763
skype:alecos.papadopoulos
11 years
gnuplot: 2nd yaxis
by Artur T.
I've got another question regarding gnuplot. At the moment gretl
automatically draws a 2nd yaxis (if it is not suppressed by the
"--single-yaxis" option) if a certain criteria is fulfilled. However, is
there a way to specify manually a separate variable (or a list of vars)
to a 2nd yaxis?
Of course one could write a function doing so; more concretely
specifying the necessary lines such as
<gnuplot>
.
.
.
set y2tics
plot \
'-' using 1:($2) axes x1y2 title "LRY (right)" w lines, \
'-' using 1:($2) axes x1y1 title "d_LRY (left)" w lines
.
.
</gnuplot>
but if it could be done within the literal-framework it much simpler...
This is not a feature request -- writing a script is quickly done as
I've got some templates for this.
Best,
Artur
11 years
