R help - Apr 2006 - difference between two density plots

Hello,

I have two densities which I plot with:

sm.density(gps)
sm.density(gps2)

Both data sets are 2D and have the same scale.

Is there a way of plotting the difference between the two density plots ?

Thank you very much,
Phil

On 4/6/2006 1:34 PM, Philipp H. Mohr wrote:
> Hello,
> 
> I have two densities which I plot with:
> 
> sm.density(gps)
> sm.density(gps2)
> 
> Both data sets are 2D and have the same scale.
> 
> Is there a way of plotting the difference between the two density plots ?
?sm.density describes the value returned by those function calls, which 
includes "the values of the density estimate at the evaluation
points".
   The evaluation points may be different between the two datasets, but 
you could use approxfun to generate functions doing linear interpolation 
for each of them, and then evaluate the density difference whereever you 
like.

Duncan Murdoch

On Thu, 6 Apr 2006, Duncan Murdoch wrote:
> On 4/6/2006 1:34 PM, Philipp H. Mohr wrote:
> > Hello,
> > 
> > I have two densities which I plot with:
> > 
> > sm.density(gps)
> > sm.density(gps2)
> > 
> > Both data sets are 2D and have the same scale.
> > 
> > Is there a way of plotting the difference between the two density
plots ?
> 
> ?sm.density describes the value returned by those function calls, which 
> includes "the values of the density estimate at the evaluation
points".
>    The evaluation points may be different between the two datasets, but 
> you could use approxfun to generate functions doing linear interpolation 
> for each of them, and then evaluate the density difference whereever you 
> like.
The eval.points can be set using sm.options(), fixing them to be the same.
> 
> Duncan Murdoch
> 
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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
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e-mail: Roger.Bivand at nhh.no