Access the cs2cs application from R

cs2cs.R

#' Access the cs2cs function from R
#'
#' @seealso http://proj4.org/index.html
#' 
#' @param x numeric or character input value for x (longitude)
#' @param y numeric or character input value for y (latitude)
#' @param from character input coordinate system definition
#' @param to character output coordinate system definition
#' @param extra character extra arguments for cs2cs
#' @param app character the fully qualified path to the cs2cs executable
#' @param charcater string of one or more elements
cs2cs <- function(x = -70.2, y = 43.8,
    from = "+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0",
    to = "+proj=lcc +lon_0=-107 +lat_0=50 +x_0=5632642.22547 +y_0=4612545.65137 +lat_1=50 +lat_2=50 +ellps=WGS84",
    extra = '-w3',
    app = Sys.which('cs2cs')){

    if (!file.exists(app[1])) stop("Application cs2cs not found")
    ff <- tempfile()
    cat(x, " ", y, "\n", sep = "", file = ff)
    CMD <- paste(app, extra, from, "+to ", to, ff)
    cat(CMD, "\n")
    r <- system(CMD, intern = TRUE)
    unlink(ff)
    strsplit(r, '[\t ]')[[1]]
}