R/SPPointstoSPLines.R

In jacpete/jpfxns: JP Functions

#' @title SpatialPoints* to SpatialLines*
#'
#' @description
#' \code{SPPointstoSPLine} creates SpatialLines or SpatialLinesDataFrame from
#' SpatialPoints or SpatialPointsDataFrame.
#'
#' @details
#' Required inputs are a SpatialPoints or SpatialPointsDataFrame, and a
#' data.frame with an "id" or "ID" field or id input parameter.
#' Some sort of id must be included. I hope a future version will remove this
#' requirement. I just don't have time now.
#'
#' @param sp SpatialPoints* object.
#' @param df datafame object for creating SpatialLinesDataFrame.
#' @param id ID vector for output line. Optional if dataframe has an 'ID' or
#' 'id' column
#' @param lineLength Logical. Should output dataframe include a column for
#' line length in meters
#'
#' @return SpatialLines* object.
#' @export
# @examples need to find test data and add examples
SPPointstoSPLines <- function(sp = NULL, df = NULL, id = NULL, lineLength = T) {
  ### SP is required
  if (is.null(sp)) {
    stop("Must Input Spatial Points Data")
  }

  ### SP must be of class
  if (class(sp) != "SpatialPoints") {
    if (class(sp) != "SpatialPointsDataFrame") {
      stop("\"sp\" Input not of class \'SpatialPoints\' or \'SpatialPointsDataFrame\'")
    }
  }
  if (is.null(df)) {
    output <- "SP"
    if (is.null(id)) {
      stop("Input is missing \"df\" and \"id\" field: Must have at least one")
    } else if (!is.null(id)) {
      if (length(id) != 1) {
        stop("Input \"id\" must have a length of 1")
      }
      ID <- id
    }
  } else {
    if (class(df) != "data.frame") {
      stop("Input \"df\" is not of class \'data.frame\'")
    }
    output <- "SPDF"
    if (!is.null(id)) {
      if (length(id) != 1) {
        stop("Input \"id\" must have a length of 1")
      }
      ID <- id
    } else if (any(c("ID", "id") %in% colnames(df))) {
      if ("ID" %in% colnames(df)) {
        ID <- df$ID[1]
      } else if ("id" %in% colnames(df)) {
        ID <- df$id[1]
      }
    } else if (is.null(id)) {
      stop("Input \"df\" does not have a column with name \'id\' or \'ID\' and Input \"id\" is NULL: Must have at least one")
    }
  }
  if (is.factor(ID)) {
    ID <- as.character(ID)
  }

  CooRS = sp@proj4string@projargs
  if (is.null(CooRS) | is.na(CooRS)) {
    stop("Issues with Coordinate System: sp@proj4string@projargs is NULL or NA")
  }


  pointcoord <- as.data.frame(coordinates(sp))
  Slo1 <- Line(pointcoord)
  Sli1<-Lines(list(Slo1),ID=ID)
  LineSP <- SpatialLines(list(Sli1), proj4string=CRS(CooRS))

  if (!is.null(df)) {
    row.names(df) <- ID
  }

  if (!is.null(df) & lineLength == T) {
    df$Length_m <- LineLength(Slo1, sum = T)
  }


  if (output == "SP") {
    return(LineSP)
  } else if (output == "SPDF") {
    LineSPDF <- SpatialLinesDataFrame(LineSP, df, match.ID = F)
    return(LineSPDF)
  }
}