R/extcalc.R

In move: Visualizing and Analyzing Animal Track Data

# calculating the extent ##works for Move and Movestack (both inherit SPDF)
setGeneric(".extcalc", function(obj, ext) standardGeneric(".extcalc"))
setMethod(
  f = ".extcalc", signature = c(obj = "SpatialPointsDataFrame", ext = "numeric"),
  definition = function(obj, ext) {
    Range <- as.vector(c(obj@bbox[1, ], obj@bbox[2, ]))
    if (length(ext) == 1) ext <- rep(ext, 4)
    if (length(ext) == 2) ext <- rep(ext, each = 2)
    if (length(ext) == 4) {
      yRange <- c(Range[3] - abs(diff(Range[3:4]) * ext[3]), Range[4] + abs(diff(Range[3:4]) *
        ext[4]))
      xRange <- c(Range[1] - abs(diff(Range[1:2]) * ext[1]), Range[2] + abs(diff(Range[1:2]) *
        ext[2]))
    } else {
      stop("The ext argument must be a vector of 1, 2 or 4 numbers")
    }
    return(c(xRange, yRange))
  }
)