[R-sig-Geo] ppp unique point coordinates?

Barry Rowlingson b.rowlingson at lancaster.ac.uk
Thu Apr 7 13:30:14 CEST 2011

On Thu, Apr 7, 2011 at 12:27 PM, francesco <francesco.pirotti at unipd.it> wrote:
> Hi everyone, I am trying to process a lot of points as ppp points, put I
> see that the ppp object cannot be created if the coordinate matrix has
> duplicated values. I have duplicates because the points are acutally
> from a 3D  laser scan survey so I will need duplicats. My code to figure
> my error was:
> pts is the x,y matrix and i is the slice that I used to check when my
> error occured.
> ppp(pts[1:i,1], pts[1:i,2], range(pts[1:i,1]), range(pts[1:i,2]))
> Question is: is there a way to overcome this? My final objective is
> "simply" to use pixellate to aggregate statistics locally (ie average
> point density in a square meter grid or mean reflectance value of each
> point)

 I get a warning, not an error, and the resultant object has all the points:

 > z = ppp(x=c(0,1,2,2)/4,y=c(1,2,3,3)/4)
Warning message:
In ppp(x = c(0, 1, 2, 2)/4, y = c(1, 2, 3, 3)/4) :
  data contain duplicated points
 > z
 planar point pattern: 4 points
window: rectangle = [0, 1] x [0, 1] units

So what's your problem?


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