# Function read.lidar
# An R function to read tiled LiDAR data for La Selva, Costa Rica in *.csv format.
# See Kellner et al. 2009 for details

# Description
# Reads a file in comma-delimited format and creates a data frame from it, with cases corresponding to lines and variables to fields in the file. 

# Usage
# read.lidar(tile.number)

# Arguments
# tile.number -- The number of the data tile to be read.  This must be an integer between 1 and 511 inclusive.

# Example
# Read tile 152 and print the first five rows
# tile152 <- read.lidar(152)
# tile152[1:5,]


read.lidar <- function(tile.number)

{

if (tile.number < 0) print("Tile number must be positive.") else

if (tile.number < 10) {lidar <- read.table(paste("tile00", tile.number, ".csv", sep=""), sep=",", 
col.names=c("EASTING","NORTHING","ELEVATION","GROUND","CLASS","RETURN","NRETURN","INTENSITY","TIME","SCANANGLE"), 
skip=1, colClasses=c("numeric", "numeric", "numeric", "numeric", "integer", "integer", "integer", "integer", "numeric", "integer"))} else

if (tile.number < 100) {lidar <- read.table(paste("tile0", tile.number, ".csv", sep=""), sep=",", 
col.names=c("EASTING","NORTHING","ELEVATION","GROUND","CLASS","RETURN","NRETURN","INTENSITY","TIME","SCANANGLE"), 
skip=1, colClasses=c("numeric", "numeric", "numeric", "numeric", "integer", "integer", "integer", "integer", "numeric", "integer"))} else

if (tile.number < 512) {lidar <- read.table(paste("tile", tile.number, ".csv", sep=""), sep=",", 
col.names=c("EASTING","NORTHING","ELEVATION","GROUND","CLASS","RETURN","NRETURN","INTENSITY","TIME","SCANANGLE"), 
skip=1, colClasses=c("numeric", "numeric", "numeric", "numeric", "integer", "integer", "integer", "integer", "numeric", "integer"))} else

print(paste("LiDAR tile number", tile.number, "does not exist.", sep=" "))

return(lidar)

}