[R] smooth scatterplot and geo map

[Greg Snow]

The usual smoothed scatterplot assumes that the x variable (longitude) is fixed and that the y-variable (latitude) is observed with error, and that the mapping is 1 to 1 or 1 to many in that for each value of x you can have at most one y value.  These assumptions don't seem to make much sense with positional data.

You might consider using xsplines instead (see ?xspline).  This draws a curve from point to point in the order of the data and the smoothness (and closeness to the points) depends are the arguments that you specify.  This makes more sense for most applications that I can think of for plotting onto a map.

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of marco
> Sent: Thursday, July 28, 2011 2:09 PM
> To: r-help at r-project.org
> Subject: [R] smooth scatterplot and geo map
> 
> Hello everybody,
> I'm trying to understand how to draw a smoothed scatterplot on a
> geographic
> map with R.
> Have a dataframe with point locations (long, lat) and was able to
> simply
> plot these points on a shp map by using the maptools package. However,
> instead of having simply the raw points on the map, I would like to
> have a
> "smoothed" scatterplot of the same superimposed on the map. Tried with
> the
> smoothScatter function, but really have no idea how to combine the map
> with
> the resulting graph.
> tx in adv
> marco
> 
> --
> View this message in context: http://r.789695.n4.nabble.com/smooth-
> scatterplot-and-geo-map-tp3702374p3702374.html
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