R/persp.loca.p.R

In orloca: Operations Research LOCational Analysis Models

#' Plots of the min-sum objective function
#'
#' \code{persp} provides a graphical representations of objetive function of the min-sum problem, which is the total weighte distance to the demand points (\code{distsum}).
#'
#' @name persp.loca.p
#'
#' @details
#' If \eqn{p<1} then \eqn{l_p} is not a norm, so only \eqn{p>=1} are valid values.
#'
#' @keywords classes hplot
#' @param x The loca.p object to compute the objective.
#' @param lp If given, then \eqn{l_p} norm will be used instead of the Euclidean norm.
#' @param xmin The minimum value for x axis.
#' @param xmax The maximum value for x axis.
#' @param ymin The minimum value for y axis.
#' @param ymax The maximum value for y axis.
#' @param n The number of divisions for grid.
#' @param ticktype parameter to pass to low level function persp
#' @param \ldots Other options.
#' @return A plot a 3D plot or min-sum function.
#' @seealso See also \code{\link{orloca-package}}, \code{\link{plot.loca.p}} and \code{\link{loca.p}}.
#' @examples
#' # A new unweighted loca.p object
#' loca <- loca.p(x = c(-1, 1, 1, -1), y = c(-1, -1, 1, 1))
#'
#' # The 3D graphics
#' persp(loca)
#'
#' @export
persp.loca.p <- function(x, lp=numeric(0), xmin=min(x@x), xmax=max(x@x), ymin=min(x@y), ymax=max(x@y), n=10, ticktype = 'detailed', ...)
{
    ## Compute graphical limits to avoid degenerated cases and wrong argument values
    .xmin = min(xmin, xmax)
    .xmax = max(xmin, xmax)
    deltax = max(.xmax - .xmin, .1)
    centerx = (.xmin + .xmax)/2
    .xmin = centerx - deltax/2
    .xmax = centerx + deltax/2
    .ymin = min(ymin, ymax)
    .ymax = max(ymin, ymax)
    deltay = max(.ymax - .ymin, .1)
    centery = (.ymin + .ymax)/2
    .ymin = centery - deltay/2
    .ymax = centery + deltay/2
    ## Build grid
    .x<-seq(.xmin, .xmax, length.out=n)
    .y<-seq(.ymin, .ymax, length.out=n)
    .z<-matrix(1, nrow=n, ncol=n, byrow=TRUE)
    ## Compute values
    if (length(lp) == 0)
    {
        for(i in 1:n)
            for(j in 1:n)
                .z[i,j] <- distsum(x, .x[i], .y[j])
    }
    else if (lp >= 1)
    {
        for(i in 1:n)
            for(j in 1:n)
                .z[i,j] <- distsumlp(x, .x[i], .y[j], p=lp)
    }
    else stop(paste(lp, gettext("is not a valid value for lp, use 1 <= lp")))
    persp(.x, .y, .z, ticktype = ticktype, ...)
    invisible(1)
}