RSAGA: SAGA Geoprocessing and Terrain Analysis in R

#' Landslide inventory and DEM
#'
#' The landslide dataset consists of landslide initiation points in the
#' \emph{Reserva Biológica San Francisco} (RBSF) area of the tropical Andes in
#' Ecuador. The landslide inventory was mapped by Stoyan (2000) in the field and
#' by the presence of landslide scars in aerial imagery. The 10 m x 10 m digital
#' elevation model (DEM) was triangulated from aerial imagery as described by
#' Jordan \emph{et al.} (2005) and provided as a courtesy of Lars Ungerechts
#' (2010).
#' 
#' Loading this dataset also loads the object \code{dem}. Existing objects named
#' \code{dem} may be overwritten.
#' 
#' Landslide data provided here are a subset of that used by Muenchow \emph{et
#' al.} (2012) to predict spatially landslide susceptibility using generalized
#' additive models (GAMs). Specifically, the here provided landslides belong to
#' the "natural" part of the \emph{RBSF} area. Please refer also to the
#' accompanying vignette for an introductory tutorial on the use of the RSAGA
#' package for terrain analysis, geoprocessing, and model-building using these
#' data.
#' @name landslides
#' @aliases dem
#' @format
#' A data frame of 1535 rows and 3 variables:
#' \itemize{
#' \item{\code{x}}: the x coordinate of the sample point
#' \item{\code{y}}: the y coordinate of the sample point
#' \item{\code{lslpts}}: this column informs if the corresponding point is a
#'   landslide (\code{TRUE}) or not (\code{FALSE}).
#' }
#' 
#' A digital elevation model as a .Rd grid \code{dem}
#' \itemize{
#' \item \code{$header} list of 8 DEM header properties
#' \item \code{$data} grid elevation values (m ASL)
#' }
#' 
#' @source \strong{DEM:}
#' 
#' Ungerechts, L. (2010): DEM 10m (triangulated from aerial photo - b/w).
#' Available online:
#' 
#' \code{http://www.tropicalmountainforest.org/data_pre.do?citid=901}
#' 
#' Jordan, E., Ungerechts, L., Caceres, B. Penafiel, A. and Francou, B. (2005):
#' Estimation by photogrammetry of the glacier recession on the Cotopaxi Volcano
#' (Ecuador) between 1956 and 1997. \emph{Hydrological Sciences}, 50, 949-961
#' 
#' \strong{Landslide Data:}
#' 
#' Muenchow, J., Brenning, A., Richter, R. (2012): Geomorphic process rates of
#' landslides along a humidity gradient in the tropical Andes, Geomorphology,
#' 139-140, 271-284
#' 
#' Stoyan, R. (2000): Aktivitat, Ursachen und Klassifikation der Rutschungen in
#' San Francisco/Südecuador. Unpublished Diploma Thesis, University of
#' Erlangen-Nuremberg, Germany.
#' @examples
#' \dontrun{
#' library("RSAGA")
#' data(landslides)
#' 
#' # Print the DEM header:
#' dem$header
#' 
#' # Write the DEM to a SAGA grid:
#' write.sgrd(data = dem, file = "dem", header = dem$header, env = env)
#' 
#' # Calculate slope of DEM:
#' rsaga.slope(in.dem = "dem", out.slope = "slope", method = "poly2zevenbergen")
#' 
#' # Pick slope values at landslide points,
#' # added to landslides data.frame as variable "slope":
#' landslides <- pick.from.saga.grid(data = landslides,
#'                                   filename = "slope",
#'                                   varname = "slope")
#' }
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