[R-sig-Geo] distance to polygon (and line_
Robert J. Hijmans
r.hijmans at gmail.com
Sun Oct 31 22:06:33 CET 2010
But if you would like to do this using longitude/latitude data, you
could try dist2Lines in 'geosphere'
library(geosphere)
dist2Line(points, SpatialPolygons)
(this function ONLY works for lon/lat, and NOT for a flat earth
coordinate system)
Robert
On Sun, Oct 31, 2010 at 1:29 PM, Rolf Turner <r.turner at auckland.ac.nz> wrote:
>
> On 1/11/2010, at 7:38 AM, Peter Larson wrote:
>
>> Hello all,
>>
>> I have a database of point (lat long) data.
>> I also have shapefiles of polygon and line data.
>>
>> I need to find the distances from each of the points to 1) the nearest
>> polygon and 2) the nearest line.
>>
>> Is this possible?
>
>
> In R all things are possible.
>
> You may have problems with units; the units in which your points are expressed
> must be the same as those in which the lines and polygons are expressed.
>
> If you can express everything in terms of two dimensional Euclidean units,
> then the facilities of spatstat will allow you to do what you want. Currently
> spatstat does not handle great circle distances.
>
> If you express your collection of polygons as a single owin object, say "xxx", then
> distfun(xxx)(x,y) will give the distances from to xxx. These will be the
> minima of the distances from the points to the individual polygons.
>
> Likewise if you express your collection of lines as a psp object, say "lll",
> then distfun(lll)(x,y) will the distance from each point to the nearest line.
>
> In the foregoing "x" represents the vector of x-coordinates of your points,
> and y the vector of y-coordinates.
>
> See
>
> vignette("shapefiles")
>
> for instructions on how to turn shapefile data into spatstat style objects.
>
> cheers,
>
> Rolf
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