# Convert Spatial Objects to WKB Converts `Spatial` objects to well-known binary (WKB ) geometry representations. ```r writeWKB(obj, endian = "little") ``` ## Arguments - `obj`: object inheriting class `Spatial`. - `endian`: The byte order (`"big"` or `"little"`) for encoding numeric types. The default is `"little"`. ## Returns A `list` with class `AsIs`. The length of the returned list is the same as the length of the argument `obj`. Each element of the returned list is a `raw` vector consisting of a WKB geometry representation. The WKB geometry type depends on the class of `obj` as shown in the table below. ||| |:--|:--| |Class of ‘obj’|Type of WKB geometry| |`SpatialPoints` or `SpatialPointsDataFrame`|Point| |`list` of `SpatialPoints` or `SpatialPointsDataFrame`|MultiPoint| |`SpatialLines` or `SpatialLinesDataFrame`|MultiLineString| |`SpatialPolygons` or `SpatialPolygonsFrame`|Polygon or MultiPolygon| A `SpatialPolygons` or `SpatialPolygonsFrame` object is represented as WKB Polygons if each `Polygons` object within it represents a single polygon; otherwise it is represented as WKB MultiPolygons. The byte order of numeric types in the returned WKB geometry representations depends on the value of the argument `endian`. Little-endian byte order is known as NDR encoding, and big-endian byte order is known as XDR encoding. When this function is run in TIBCO Enterprise Runtime for R (TERR ), the return value has the SpotfireColumnMetaData attribute set to enable TIBCO Spotfire to recognize it as a WKB geometry representation. ## Details The argument `obj` may be an object of class `SpatialPoints`, `SpatialPointsDataFrame`, `SpatialLines`, `SpatialLinesDataFrame`, `SpatialPolygons`, or `SpatialPolygonsDataFrame`, or a `list` in which each element is an object of class `SpatialPoints` or `SpatialPointsDataFrame`. ## Examples ```r # load package sp library(sp) # create an object of class SpatialPoints x = c(1, 2) y = c(3, 2) obj <- SpatialPoints(data.frame(x, y)) # convert to WKB Point wkb <- writeWKB(obj) # create a list of objects of class SpatialPoints x1 = c(1, 2, 3, 4, 5) y1 = c(3, 2, 5, 1, 4) x2 <- c(9, 10, 11, 12, 13) y2 <- c(-1, -2, -3, -4, -5) Sp1 <- SpatialPoints(data.frame(x1, y1)) Sp2 <- SpatialPoints(data.frame(x2, y2)) obj <- list("a"=Sp1, "b"=Sp2) # convert to WKB MultiPoint wkb <- writeWKB(obj) # create an object of class SpatialLines l1 <- data.frame(x = c(1, 2, 3), y = c(3, 2, 2)) l1a <- data.frame(x = l1[, 1] + .05, y = l1[, 2] + .05) l2 <- data.frame(x = c(1, 2, 3), y = c(1, 1.5, 1)) Sl1 <- Line(l1) Sl1a <- Line(l1a) Sl2 <- Line(l2) S1 <- Lines(list(Sl1, Sl1a), ID = "a") S2 <- Lines(list(Sl2), ID = "b") obj <- SpatialLines(list(S1, S2)) # convert to WKB MultiLineString wkb <- writeWKB(obj) # create an object of class SpatialPolygons triangle <- Polygons( list( Polygon(data.frame(x = c(2, 2.5, 3, 2), y = c(2, 3, 2, 2))) ), "triangle") rectangles <- Polygons( list( Polygon(data.frame(x = c(0, 0, 1, 1, 0), y = c(0, 1, 1, 0, 0))), Polygon(data.frame(x = c(0, 0, 2, 2, 0), y = c(-2, -1, -1, -2, -2))) ), "rectangles") obj <- SpatialPolygons(list(triangle, rectangles)) # convert to WKB MultiPolygon wkb <- writeWKB(obj) # use the WKB as a column in a data frame ds <- data.frame(ID = c("a","b"), Geometry = wkb) # calculate envelope columns and cbind to the data frame coords <- writeEnvelope(obj) ds <- cbind(ds, coords) ``` ## See Also `writeEnvelope`, `readWKB`

writeWKB function