On Mon, 10 Jul 2017, Sven Schreiber wrote:
Am 10.07.2017 um 17:09 schrieb Allin Cottrell:
> I now see what's happening here. We get the lag reporting right in the
> So we need a more robust heuristic. But in the Q/M case it's kinda
> strange to include less than 3 lags: that invites numerical
> problems since the optimizer doesn't have enough lags to figure out
> the shape of the decay function.
OK, granted. However I think there are special cases (of Almon?)
where you can reduce the whole thing to a single parameter? So it's
not always absurd to have only two or even one lag.
Number of parameters has nothing to do with number of lags (unless
you're doing "unrestricted MIDAS"). The point is that you have a
parsimonious parameterization, generally just one or two
hyperparameters, and as many lags as you like. Extra lags don't eat up
degrees of freedom, there's no reason of parsimony to limit the number
tightly, and you want a reasonable number of them to identify the
hyperparameter(s).
Anyway, there's now a fix in git and snapshots for the mis-reporting
of the min and max midas lags when the number of lags is very small.
The fix depends on recording one more piece of metadata concerning
midas series, and to get this working it's probably necessary to
regenerate derivative series such as log differences and lags. The
supplied gdp_midas dataset is now updated to the new spec, and the
following reports the lags correctly:
<hansl>
open gdp_midas.gdt -q
list dX = ld_payems*
list dXL1 = hflags(1, 2, dX)
list dXL2 = hflags(2, 3, dX)
matrix theta = {1,5}
smpl 1985:1 2009:1
midasreg ld_qgdp 0 ld_qgdp(-1) ; mdsl(dXL1, 1, theta)
midasreg ld_qgdp 0 ld_qgdp(-1) ; mdsl(dXL2, 1, theta)
midasreg ld_qgdp 0 ld_qgdp(-1) ; mds(dX, 2, 3, 1, theta)
</hansl>
And since we're at the Midas stuff, two more remarks:
a) I have a quarterly workfile with some (monthly) Midas lists in
there, and in particular the following series (with ID numbers):
4 ld_orders_m3
5 ld_orders_m2
6 ld_orders_m1
7 BIPnom
When I click on one of 4/5/6, everything 4-7 gets selected, where I
expect only 4-6. I am, however, able to click on ID7 and get only
ID7 selected. (With 4-7 selected I can also ctrl-click on ID7 to
unselect that.)
OK, I see what you mean: the midas-list status is somehow bleeding
over onto the following series. Should be a fix soon.
b) When I right-click on a Midas group/list and click on "time
series plot" I get one plot. It took me a while to realize that it's
a hi-freq (monthly) plot. Perhaps the x-axis could be automatically
labeled with "months" (=the hi-freq unit) or something like that.
Yes, good idea.
Allin