R/gc.velocity.R

In mdsumner/mdsutils: Miscellaneous tools for sumnerd.

#' gc velocity
#' 
#' %% ~~ A concise (1-5 lines) description of what the function does. ~~
#' 
#' %% ~~ If necessary, more details than the description above ~~
#' 
#' @param tr %% ~~Describe \code{tr} here~~
#' @return %% ~Describe the value returned %% If it is a LIST, use %%
#' \item{comp1 }{Description of 'comp1'} %% \item{comp2 }{Description of
#' 'comp2'} %% ...
#' @note %% ~~further notes~~
#' @author %% ~~who you are~~
#' @seealso %% ~~objects to See Also as \code{\link{help}}, ~~~
#' @references %% ~put references to the literature/web site here ~
#' @keywords ~kwd1 ~kwd2
#' @examples
#' 
#' ##---- Should be DIRECTLY executable !! ----
#' ##-- ==>  Define data, use random,
#' ##--	or do  help(data=index)  for the standard data sets.
#' 
#' ## The function is currently defined as
#' function(tr) {
#' 
#'   p <- as.matrix(tr[,c("Lat","Lon")])
#'   dt <- diff(unclass(tr$Time)/(24*60*60))
#'   n <- nrow(p)
#'   gc.dist(p[-n,],p[-1,])/dt
#'   }
#' 
gc.velocity <-
function(tr) {

  p <- as.matrix(tr[,c("Lat","Lon")])
  dt <- diff(unclass(tr$Time)/(24*60*60))
  n <- nrow(p)
  gc.dist(p[-n,],p[-1,])/dt
}