Hi Jose,
If I understand correctly, some of the points lie outside of the polygons,
but you want to pick up the information for the nearest associated
polygon?
I think the easiest thing to do would be to put a buffer around each of the
points (you could specify 50 m if it is in projected coordinates),
converting them to polygons, and then your task becomes an intersection of
two different polygon objects.
I haven't done this type of operation in R, but I suspect you could find
your answer with the following functions:
library(sp)
?over
library(rgeos)
?gBuffer
?gIntersects
I suggest putting up a subset of your data illustrating the problem, and
then maybe someone else who has a better idea on polygon to polygon
intersects/overlays could suggest the method.
Cheers, Lyndon
On Tue, Jan 10, 2012 at 3:33 PM, Jose Bustos Melo <jbustosm...@yahoo.es>wrote:
> Hi Lyndon,
>
> I really apreciate you help. Your function was very helpfull. However, in
> this case polygons are block (block where many homes are). The avenue and
> street aren't assigned at any polygon, so if a point is out of a polygon is
> there any way to get it inside the nearest polygon?. For example, any point
> near (50 meters) the polygon should correspond to that polygon. So, it this
> way I could change the precision of the estimation, don't you?
>
> Than you in advance!
> José
>
> ------------------------------
> *De:* Lyndon Estes <lyndon.es...@gmail.com>
> *Para:* Jose Bustos Melo <jbustosm...@yahoo.es>
> *CC:* "r-sig-geo@r-project.org" <r-sig-geo@r-project.org>
> *Enviado:* martes 10 de enero de 2012 15:21
> *Asunto:* Re: [R-sig-Geo] Spatial join using shapefiles with R
>
> Hi Jose,
>
> This function might help with what you want to do.
>
> Cheers, Lyndon
>
> IntersectPtWithPoly <- function(x, y) {
> # Extracts values from a SpatialPolygonDataFrame with
> SpatialPointsDataFrame, and appends table (similar to
> # ArcGIS intersect)
> # Args:
> # x: SpatialPoints*Frame
> # y: SpatialPolygonsDataFrame
> # Returns:
> # SpatialPointsDataFrame with appended table of polygon attributes
>
> # Set up overlay with new column of join IDs in x
> z <- overlay(y, x)
>
> # Bind captured data to points dataframe
> x2 <- cbind(x, z)
>
> # Make it back into a SpatialPointsDataFrame
> # Account for different coordinate variable names
> if(("coords.x1" %in% colnames(x2)) & ("coords.x2" %in% colnames(x2))) {
> coordinates(x2) <- ~coords.x1 + coords.x2
> } else if(("x" %in% colnames(x2)) & ("x" %in% colnames(x2))) {
> coordinates(x2) <- ~x + y
> }
>
> # Reassign its projection if it has one
> if(is.na(CRSargs(x@proj4string)) == "FALSE") {
> x2@proj4string <- x@proj4string
> }
> return(x2)
> }
>
>
>
>
> On Tue, Jan 10, 2012 at 1:06 PM, Jose Bustos Melo <jbustosm...@yahoo.es>wrote:
>
> Hi everyone,
>
> Its have been very difficult to do an spatial join with R and I couldn't
> find any good manual about it. So, I will explain it if someone is willing
> to help.
>
> I have one Shapefile with poligons (with its number) and another Shapefile
> with xy points. My idea is to obtain the number of the polygons where the
> points are found, in order to obtain their social data of those polygons.
>
> How can I do it? Is there any good way to do it? Where can I find
> informationa bout it? Any function?
>
> Thanks in advance
> José
>
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>
>
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>
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