How to do square buffers around spatial points

Dear list members,

Ho can I do square buffers around spatial points?

2016-08-25 13:01 GMT+01:00 Manuel Sp?nola <mspinola10 at gmail.com>:

Dear list members,

Ho can I do square buffers around spatial points?

Break it down:

1. For each point compute the coordinates of the four corners of the
square by adding half the width of your square.
2. Construct a Polygon from those four points for each of your source points.
3. Build a SpatialPolygons object from all your Polygons.

How far can you get with it now?

Barry

Here's a one-liner:

# for some SpatialPointsDataFrame `d`, and some half-width `w`, this
produces a set of square SpatialPolygons
# with square height and width equal to 2*w:

polys = SpatialPolygons(apply(apply(coordinates(d),1,function(r){
cbind(r+c(w,w),r+c(w,-w),r+c(-w,-w),r+c(-w,w),r+c(w,w))}),2,
function(v){Polygons(list(Polygon(matrix(v,ncol=2,byrow=
TRUE))),ID=runif(1))}))

 > plot(polys)
 > plot(d,add=TRUE)

Barry



On Thu, Aug 25, 2016 at 2:11 PM, Barry Rowlingson
<b.rowlingson at lancaster.ac.uk> wrote:

2016-08-25 13:01 GMT+01:00 Manuel Sp?nola <mspinola10 at gmail.com>:

Dear list members,

Ho can I do square buffers around spatial points?

Break it down:

1. For each point compute the coordinates of the four corners of the
square by adding half the width of your square.
2. Construct a Polygon from those four points for each of your source

points.

3. Build a SpatialPolygons object from all your Polygons.

How far can you get with it now?

Barry