[Gretl-devel] some function suggestions/questions

Allin Cottrell cottrell at wfu.edu
Wed Jul 29 19:30:20 EDT 2009


On Wed, 29 Jul 2009, Sven Schreiber wrote:

> Allin Cottrell schrieb:
> > On Mon, 20 Jul 2009, Allin Cottrell wrote:
> >
> >> Revision to what I said before: pergm() takes either one or two
> >> arguments, the first being a series (or conformable matrix) and
> >> the optional second one being an integer bandwidth for use
> >> with the Bartlett kernel.  If the second arg is omitted you get
> >> the sample periodogram.
> >>
> >> The returned matrix has 3 columns: omega in 1, the "periods" as
> >> printed by the pergm command in col2, and the density in col 3.
> >
> > On third thoughts, we probably should not include the "periods"
> > column in the pergm function output -- omega plus density is
> > cleaner.  Anyone?
>
> I agree, having only one set of the x- and y-values of the corresponding
> x/y-graph is more transparent.

Thanks.  In the absence of disagreement I went ahead and
implemented this in CVS.

> On a slightly different point, I'm just wondering whether the
> number of distinct omega values to return should be a function
> argument, too? What I mean is something like:
>
> pergm(x,10,100) -- would mean that the returned matrix has 100 rows
> pergm(x,10) -- gives you the current default value

Sven, I think you're implying that the current default is 10 rows.
In fact it's T/2, where T is the length of the current sample
after adjusting for any missing values.  I think this is
reasonable, and if we're going to go further in terms of
user-level customization that might fairly be confined to the
fft() function.

Allin.


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