over-methods | R Documentation |
consistent spatial overlay for points, grids and polygons: at the spatial locations of object x retrieves the indexes or attributes from spatial object y
over(x, y, returnList = FALSE, fn = NULL, ...)
x %over% y
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 |
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
.
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.
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 the x
points falling
in each polygon (set) of y
returns a data.frame of the second argument with row entries corresponding to the first argument
returns
the polygon index of points in y
; if x
is
a SpatialPolygonsDataFrame
, a data.frame with rows from
x
corresponding to points in y
is returned.
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.
returns grid values x at spatial point locations y; NA for NA grid cells or points outside the grid
returns grid values x at spatial point locations y; NA for NA grid cells or points outside the grid
returns grid values x at spatial point locations y; NA for NA grid cells or points outside the grid
xx
xx
xx
xx
xx
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.
Edzer Pebesma, edzer.pebesma@uni-muenster.de
vignette("over")
for examples and figures
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