R/xyz2dataframe.prevR.r

In larmarange/prevR: Estimating Regional Trends of a Prevalence from a DHS and Similar Surveys

#' Convert a surface in xyz to a data frame.
#'
#' Several functions (for example [KernSmooth::bkde2D()])
#' return a surface as a list "xyz" composed of three elements:
#' vector of ordinates in the x dimension,
#' vector of ordinates in the y dimension and
#' a matrix with the values of the surface in x and y.
#' This function transforms a list "xyz" into a data frame.
#'
#' @param xyz a list with 3 elements: a vector with x-coordinates,
#'   a vector with y-coordinates and
#'   and matrix with value for each point of coordinates `x[i], y[j]`.
#' @param xcol x index.
#' @param ycol y index.
#' @param zcol z index.
#'
#' @note \code{xyz} could be a list like \code{x,y,z1,z2,z3}.
#' If so, \code{zcol} should be equal
#' to \code{c("z1","z2","z3")} or \code{c(3,4,5)}.
#'
#' @return A \code{data.frame}.
#'
#' @examples
#' x <- matrix(c(2, 4, 6, 8, 10, 2, 4, 6, 8, 10), ncol = 2)
#' op <- KernSmooth::bkde2D(x, bandwidth = 1)
#' str(op)
#'
#' op.df <- xyz2dataframe(op)
#' str(op.df)
#'
#' @keywords manip spatial
#' @export

# Transforme une liste de 3 elements (x, y et z) comme le resultat de bkde2D
# en un data.frame
# note : z peut etre une liste de matrices
xyz2dataframe <- function(xyz, xcol = 1, ycol = 2, zcol = 3) {
  nx <- length(xyz[[xcol]])
  ny <- length(xyz[[ycol]])
  for (i in 1:ny) {
    z <- xyz[zcol]
    for (k in seq_len(length(zcol))) {
      z[[k]] <- z[[k]][, i]
    }
    y <- rep(xyz[[ycol]][i], nx)
    x <- xyz[xcol]
    temp <- data.frame(x, y, z)
    names(temp) <- c(names(xyz[xcol]), names(xyz[ycol]), names(xyz[zcol]))
    if (i == 1) {
      res <- temp
    } else {
      res <- rbind(res, temp)
    }
  }
  return(res)
}