1\name{SpatialLinesMidPoints} 2\alias{SpatialLinesMidPoints} 3%- Also NEED an '\alias' for EACH other topic documented here. 4\title{Line midpoints} 5\description{ 6The function onverts SpatialLinesDataFrame to SpatialPointsDataFrame with points at the midpoints of the line segments. 7} 8\usage{ 9SpatialLinesMidPoints(sldf) 10} 11%- maybe also 'usage' for other objects documented here. 12\arguments{ 13 \item{sldf}{A SpatialLines or SpatialLinesDataFrame object} 14} 15\details{ 16The function builds a SpatialPointsDataFrame from the midpoints of Line objects belonging to Lines objects in an object inheriting from a Spatial Lines object. The output data slot contains an index variable showing which Lines object the midpoints belong to. 17} 18 19\value{ 20 A SpatialPointsDataFrame object created from the input object. 21} 22 23\author{Jonathan Callahan, modified by Roger Bivand} 24 25\examples{ 26xx <- readShapeLines(system.file("shapes/fylk-val.shp", package="maptools")[1], 27 proj4string=CRS("+proj=utm +zone=33 +datum=WGS84")) 28plot(xx, col="blue") 29spdf <- SpatialLinesMidPoints(xx) 30plot(spdf, col="orange", add=TRUE) 31} 32 33\keyword{spatial} 34 35