over-methods {sp} | R Documentation |
consistent spatial overlay for points, grids and polygons
Description
consistent spatial overlay for points, grids and polygons: at the spatial locations of object x retrieves the indexes or attributes from spatial object y
Usage
over(x, y, returnList = FALSE, fn = NULL, ...)
x %over% y
Arguments
x |
geometry (locations) of the queries |
y |
layer from which the geometries or attributes are queried |
returnList |
logical; see value |
fn |
(optional) a function; see value |
... |
arguments passed on to function |
Value
If y
is only geometry an object of length length(x)
.
If returnList
is FALSE
, a vector with the (first) index
of y
for each geometry (point, grid cell centre, polygon
or lines) matching x
. if returnList
is TRUE, a list of
length length(x)
, with list element i
the vector of
all indices of the geometries in y
that correspond to the
$i$-th geometry in x
.
If y
has attribute data, attribute data are
returned. returnList
is FALSE, a data.frame
with
number of rows equal to length(x)
is returned, if it is
TRUE a list with length(x)
elements is returned, with a list
element the data.frame
elements of all geometries in y
that correspond to that element of x
.
Methods
- x = "SpatialPoints", y = "SpatialPolygons"
returns a numeric vector of length equal to the number of points; the number is the index (number) of the polygon of
y
in which a point falls; NA denotes the point does not fall in a polygon; if a point falls in multiple polygons, the last polygon is recorded.- x = "SpatialPointsDataFrame", y = "SpatialPolygons"
equal to the previous method, except that an argument
fn=xxx
is allowed, e.g.fn = mean
which will then report a data.frame with the mean attribute values of thex
points falling in each polygon (set) ofy
- x = "SpatialPoints", y = "SpatialPolygonsDataFrame"
returns a data.frame of the second argument with row entries corresponding to the first argument
- x = "SpatialPolygons", y = "SpatialPoints"
returns the polygon index of points in
y
; ifx
is aSpatialPolygonsDataFrame
, a data.frame with rows fromx
corresponding to points iny
is returned.- x = "SpatialGridDataFrame", y = "SpatialPoints"
returns object of class SpatialPointsDataFrame with grid attribute values x at spatial point locations y; NA for NA grid cells or points outside grid, and NA values on NA grid cells.
- x = "SpatialGrid", y = "SpatialPoints"
returns grid values x at spatial point locations y; NA for NA grid cells or points outside the grid
- x = "SpatialPixelsDataFrame", y = "SpatialPoints"
returns grid values x at spatial point locations y; NA for NA grid cells or points outside the grid
- x = "SpatialPixels", y = "SpatialPoints"
returns grid values x at spatial point locations y; NA for NA grid cells or points outside the grid
- x = "SpatialPoints", y = "SpatialGrid"
xx
- x = "SpatialPoints", y = "SpatialGridDataFrame"
xx
- x = "SpatialPoints", y = "SpatialPixels"
xx
- x = "SpatialPoints", y = "SpatialPixelsDataFrame"
xx
- x = "SpatialPolygons", y = "SpatialGridDataFrame"
xx
Note
over
can be seen as a left outer join in SQL; the
match is a spatial intersection.
points on a polygon boundary and points corresponding to a polygon vertex are considered to be inside the polygon.
These methods assume that pixels and grid cells are never
overlapping; for objects of class SpatialPixels
this is
not guaranteed.
Author(s)
Edzer Pebesma, edzer.pebesma@uni-muenster.de
See Also
vignette("over")
for examples and figures