overlay {sp} | R Documentation

## spatial overlay for points, grids and rings

### Description

### Usage

    overlay(x, y, ...)

### Arguments

`x` | first layer
`y` | second layer, put on top of x
`...` | optional arguments; see example below

### Value

a numerical array of indices of `x` on locations of `y`, or a data.frame with (possibly aggregate) properties of `x` in units of `y`.

### Note

points on a ring boundary and points corresponding to a ring vertex are considered to be inside the ring

### See Also

overlay-methods, point.in.polygon

### Examples

    r1 = cbind(c(180114, 180553, 181127, 181477, 181294, 181007, 180409,
    180162, 180114), c(332349, 332057, 332342, 333250, 333558, 333676,
    332618, 332413, 332349))
    r2 = cbind(c(180042, 180545, 180553, 180314, 179955, 179142, 179437,
    179524, 179979, 180042), c(332373, 332026, 331426, 330889, 330683,
    331133, 331623, 332152, 332357, 332373))
    r3 = cbind(c(179110, 179907, 180433, 180712, 180752, 180329, 179875,
    179668, 179572, 179269, 178879, 178600, 178544, 179046, 179110),
    c(331086, 330620, 330494, 330265, 330075, 330233, 330336, 330004,
    329783, 329665, 329720, 329933, 330478, 331062, 331086))

    sr1=Polygons(list(Polygon(r1)),"r1")
    sr2=Polygons(list(Polygon(r2)),"r2")
    sr3=Polygons(list(Polygon(r3)),"r3")
    sr=SpatialPolygons(list(sr1,sr2,sr3))
    srdf=SpatialPolygonsDataFrame(sr, data.frame(cbind(1:3,5:3), row.names=c("r1","r2","r3")))

    data(meuse)
    coordinates(meuse) = ~x+y
    data(meuse.grid)
    coordinates(meuse.grid) = ~x+y
    gridded(meuse.grid) = TRUE

    plot(meuse)
    polygon(r1)
    polygon(r2)
    polygon(r3)

    overlay(srdf, meuse)
    overlay(sr, meuse)

    overlay(meuse, srdf, fn = mean)
    overlay(meuse, srdf)
    overlay(as(meuse, "SpatialPoints"), srdf)
    overlay(as(meuse, "SpatialPoints"), sr)

    # same thing, with grid:
    overlay(srdf, meuse.grid)
    overlay(sr, meuse.grid)

    overlay(meuse.grid, srdf, fn = mean)
    overlay(meuse.grid, srdf)
    overlay(as(meuse.grid, "SpatialPoints"), srdf)
    overlay(as(meuse.grid, "SpatialPoints"), sr)

[Package sp version 0.7-12 Index]