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#' @title Manipulate graph
#' @description functions to manipulate a graph
#'
#' @param g igraph object
#' @param attr edge attribute name used to sort edges
#' @param desc logical. sort in descending (default) or ascending order
#' @details `reorder_edges()` allows to reorder edges according to an attribute so that edges are
#' drawn in the given order.
#' @name graph_manipulate
#' @return manipulated graph
#' @examples
#' library(igraph)
#'
#' g <- sample_gnp(10, 0.5)
#' E(g)$attr <- 1:ecount(g)
#' gn <- reorder_edges(g,"attr")
#'
#' @author David Schoch
NULL
#' @rdname graph_manipulate
#' @export
reorder_edges <- function(g, attr, desc = TRUE) {
if (!"name" %in% igraph::vertex_attr_names(g)) {
igraph::V(g)$name <- 1:igraph::vcount(g)
}
edges_df <- igraph::as_data_frame(g, what = "edges")
edges_df <- edges_df[order(edges_df[[attr]], decreasing = desc), ]
vertices <- igraph::as_data_frame(g, what = "vertices")
vattrs <- igraph::vertex_attr_names(g)
idname <- which(vattrs == "name")
vertices <- vertices[, c(idname, setdiff(seq_along(vattrs), idname))]
gn <- igraph::graph_from_data_frame(
d = edges_df,
directed = igraph::is_directed(g),
vertices = vertices
)
gn
}
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