R/area_cubierta.R

In PabloMBooster/vmsR: For analysing VMS data

area_cubierta <- function(dc, lat, grado) {

  grado <- grado
  dc    <- dc
  lat   <- lat

  intervalos <- (-18.5+3)/(-grado)

  y.tot<-NULL
  for (i in 1:intervalos)
  {
    y <- matrix(cbind(rep(-3-(grado)*(i-1),40),rep(-3-(grado)*i,40)),ncol=2)
    y.tot <- rbind(y.tot,y)
  }

  x.tot <- matrix(cbind(rep(seq(0,195,by=5),dim(y.tot)[1]/40),
                        rep(seq(5,200,by=5),dim(y.tot)[1]/40)),ncol=2)

  xy <- data.frame(cbind(x.tot,y.tot))
  names(xy)<-c("x1","x2","y1","y2")
  xy$num.area <- 1:dim(xy)[1]

  data <- data.frame(cbind(dc=dc,lat=lat))
  name_area <- NULL

  suppressWarnings({for(j in 1:length(dc))
  {
    pos <- data[j,]

    xy$diffx <- NULL
    xy$diffy <- NULL

    xy$diffx = abs(pos$dc - xy$x1 + pos$dc - xy$x2)
    xy$diffy = abs(pos$lat - xy$y1 + pos$lat - xy$y2)
    xy$diffxy = xy$diffy + xy$diffx
    id <- xy[xy$diffxy==min(xy$diffxy),"num.area"]

    name_area <- rbind(name_area,id)
  } })
  dimnames(name_area) <- NULL
  name_area <- as.numeric(name_area)
  area       <- length(unique(name_area))*60*grado*60*grado
  return(list(name_area = name_area, area = area))
}