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Re: st: grid point

From   "Austin Nichols" <[email protected]>
To   [email protected]
Subject   Re: st: grid point
Date   Wed, 23 Jan 2008 08:22:13 -0500

xinzheng shi <[email protected]>:

I would have guessed you were using -lpoly- where the default is
min(50,_N) but you can specify the number of points via an option.  If
you are looking to have a certain "overlap" across grid points given a
bandwidth, or nonstandard spacing of grid points, you can make you own
series of grid points x and use the gen(f) at(x) options.

sysuse auto
su wei
g lnw=exp((ln(r(max))-ln(r(min)))/20*(_n-1)+ln(r(min))) in 1/21
lpoly mpg wei, gen(m) at(lnw) nogr
line m lnw

On Jan 23, 2008 4:22 AM, Maarten buis <[email protected]> wrote:
> --- xinzheng shi <[email protected]> wrote:
> >   I would like to know how to identify the number of
> > grid point in the nonparametric graph. I know the
> > usual way to identify the bandwidth is
> > 0.9*sd*N^(-0.2). But is there any formular to link
> > bandwidth with number of grid points given that
> > observation number is N.
> You don't tell us what nonparametric graph you are
> talking about (there are many, e.g. -twoway fpfit-,
> -twoway mband-) but given your reference to
> bandwidth I assume you are talking about -lowess-.
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