`over.Rd`

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

`fn`

, except for the special argument`minDimension`

: minimal dimension for an intersection to be counted; -1 takes any intersection, and does not order; 0 takes any intersection but will order according to dimensionality of the intersections (if returnList is TRUE, 1 (2) selects intersections with dimension 1, meaning lines (2, meaning areas); see`vignette("over")`

for details

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`

.

- 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 the`x`

points falling in each polygon (set) of`y`

- 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`

; if`x`

is a`SpatialPolygonsDataFrame`

, a data.frame with rows from`x`

corresponding to points in`y`

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

`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.

`vignette("over")`

for examples and figures