R/geom_edge_hive.R

In YTLogos/ggraph: An Implementation of Grammar of Graphics for Graphs and Networks

#' Draw edges in hive plots
#'
#' This geom is only intended for use together with the hive layout. It draws
#' edges between nodes as bezier curves, with the control points positioned at
#' the same radi as the start or end point, and at a distance defined by the
#' curvature argument.
#'
#' @details
#' Many geom_edge_* layers comes in 3 flavors depending on the level of control
#' needed over the drawing. The default (no numeric postfix) generate a number
#' of points (\code{n}) along the edge and draws it as a path. Each point along
#' the line has a numeric value associated with it giving the position along the
#' path, and it is therefore possible to show the direction of the edge by
#' mapping to this e.g. \code{colour = ..index..}. The version postfixed with a
#' "2" uses the "long" edge format (see \code{\link{get_edges}}) and makes it
#' possible to interpolate node parameter between the start and end node along
#' the edge. It is considerable less performant so should only be used if this
#' is needed. The version postfixed with a "0" draws the edge in the most
#' performant way, often directly using an appropriate grob from the grid
#' package, but does not allow for gradients along the edge.
#'
#' Often it is beneficial to stop the drawing of the edge before it reaches the
#' node, for instance in cases where an arrow should be drawn and the arrowhead
#' shouldn't lay ontop or below the node point. geom_edge_* and geom_edge_*2
#' supports this through the start_cap and end_cap aesthetics that takes a
#' \code{\link{geometry}} specification and dynamically caps the termini of the
#' edges based on the given specifications. This means that if
#' \code{end_cap = circle(1, 'cm')} the edges will end at a distance of 1cm even
#' during resizing of the plot window.
#'
#' All \code{geom_edge_*} and \code{geom_edge_*2} have the ability to draw a
#' label along the edge. The reason this is not a separate geom is that in order
#' for the label to know the location of the edge it needs to know the edge type
#' etc. Labels are drawn by providing a label aesthetic. The label_pos can be
#' used to specify where along the edge it should be drawn by supplying a number
#' between 0 and 1. The label_size aesthetic can be used to control the size of
#' the label. Often it is needed to have the label written along the direction
#' of the edge, but since the actual angle is dependent on the plot dimensions
#' this cannot be calculated beforehand. Using the angle_calc argument allows
#' you to specify whether to use the supplied angle aesthetic or whether to draw
#' the label along or across the edge.
#'
#' @note In order to avoid excessive typing edge aesthetic names are
#' automatically expanded. Because of this it is not necessary to write
#' \code{edge_colour} within the \code{aes()} call as \code{colour} will
#' automatically be renamed appropriately.
#'
#' @section Aesthetics:
#' geom_edge_hive and geom_edge_hive0 understand the following
#' aesthetics. Bold aesthetics are automatically set, but can be overridden.
#' \itemize{
#'  \item{\strong{x}}
#'  \item{\strong{y}}
#'  \item{\strong{xend}}
#'  \item{\strong{yend}}
#'  \item{edge_colour}
#'  \item{edge_width}
#'  \item{edge_linetype}
#'  \item{edge_alpha}
#'  \item{filter}
#' }
#' geom_edge_hive2 understand the following aesthetics. Bold aesthetics are
#' automatically set, but can be overridden.
#' \itemize{
#'  \item{\strong{x}}
#'  \item{\strong{y}}
#'  \item{\strong{group}}
#'  \item{edge_colour}
#'  \item{edge_width}
#'  \item{edge_linetype}
#'  \item{edge_alpha}
#'  \item{filter}
#' }
#' geom_edge_hive and geom_edge_hive2 furthermore takes the following
#' aesthetics.
#' \itemize{
#'   \item{start_cap}
#'   \item{end_cap}
#'   \item{label}
#'   \item{label_pos}
#'   \item{label_size}
#'   \item{angle}
#'   \item{hjust}
#'   \item{vjust}
#'   \item{family}
#'   \item{fontface}
#'   \item{lineheight}
#' }
#'
#' @section Computed variables:
#'
#' \describe{
#'  \item{index}{The position along the path (not computed for the *0 version)}
#' }
#'
#'
#' @inheritParams geom_edge_link
#' @inheritParams ggplot2::geom_path
#'
#' @param curvature The curvature of the bezier. Defines the distance from the
#' control points to the midpoint between the start and end node. 1 means the
#' control points are positioned midway between the nodes, while 0 means it
#' coincide with the nodes (resulting in straight lines)
#'
#' @author Thomas Lin Pedersen
#'
#' @family geom_edge_*
#'
#' @examples
#' # Plot the flare import graph as a hive plot
#' library(igraph)
#' flareGr <- graph_from_data_frame(flare$imports)
#'
#' # Add some metadata to divide nodes by
#' V(flareGr)$type <- 'Both'
#' V(flareGr)$type[degree(flareGr, mode = 'in') == 0] <- 'Source'
#' V(flareGr)$type[degree(flareGr, mode = 'out') == 0] <- 'Sink'
#'
#' analyticsNodes <- grep('flare.analytics', V(flareGr)$name)
#' E(flareGr)$type <- 'Other'
#' E(flareGr)[inc(analyticsNodes)]$type <- 'Analytics'
#'
#' ggraph(flareGr, 'hive', axis = 'type') +
#'   geom_edge_hive(aes(colour = type), edge_alpha = 0.1) +
#'   coord_fixed()
#'
#' @rdname geom_edge_hive
#' @name geom_edge_hive
#'
NULL

#' @rdname ggraph-extensions
#' @format NULL
#' @usage NULL
#' @importFrom ggforce StatBezier
#' @export
StatEdgeHive <- ggproto('StatEdgeHive', StatBezier,
    setup_data = function(data, params) {
        if (any(names(data) == 'filter')) {
            if (!is.logical(data$filter)) {
                stop('filter must be logical')
            }
            data <- data[data$filter, names(data) != 'filter']
        }
        data$group <- seq_len(nrow(data))
        data2 <- data
        data2$x <- data2$xend
        data2$y <- data2$yend
        data$xend <- NULL
        data$yend <- NULL
        data2$xend <- NULL
        data2$yend <- NULL
        keep <- atan2(data$y, data$x) != atan2(data2$y, data2$x)
        createHiveBezier(data[keep, ], data2[keep, ], params)
    },
    required_aes = c('x', 'y', 'xend', 'yend'),
    default_aes = aes(filter = TRUE),
    extra_params = c('na.rm', 'n', 'curvature')
)
#' @rdname geom_edge_hive
#'
#' @export
geom_edge_hive <- function(mapping = NULL, data = get_edges(),
                           position = "identity", arrow = NULL,
                           curvature = 0.5, n = 100, lineend = "butt",
                           linejoin = "round", linemitre = 1,
                           label_colour = 'black',  label_alpha = 1,
                           label_parse = FALSE, check_overlap = FALSE,
                           angle_calc = 'rot', force_flip = TRUE,
                           label_dodge = NULL, label_push = NULL,
                           show.legend = NA, ...) {
    mapping <- completeEdgeAes(mapping)
    mapping <- aesIntersect(mapping, aes_(x=~x, y=~y, xend=~xend, yend=~yend))
    layer(data = data, mapping = mapping, stat = StatEdgeHive,
          geom = GeomEdgePath, position = position, show.legend = show.legend,
          inherit.aes = FALSE,
          params = expand_edge_aes(
              list(arrow = arrow, lineend = lineend, linejoin = linejoin,
                   linemitre = linemitre, na.rm = FALSE, n = n,
                   interpolate = FALSE, curvature = curvature,
                   label_colour = label_colour, label_alpha = label_alpha,
                   label_parse = label_parse, check_overlap = check_overlap,
                   angle_calc = angle_calc, force_flip = force_flip,
                   label_dodge = label_dodge, label_push = label_push, ...)
          )
    )
}
#' @rdname ggraph-extensions
#' @format NULL
#' @usage NULL
#' @importFrom ggforce StatBezier2
#' @export
StatEdgeHive2 <- ggproto('StatEdgeHive2', StatBezier2,
    setup_data = function(data, params) {
        if (any(names(data) == 'filter')) {
            if (!is.logical(data$filter)) {
                stop('filter must be logical')
            }
            data <- data[data$filter, names(data) != 'filter']
        }
        data <- data[order(data$group),]
        data2 <- data[c(FALSE, TRUE), ]
        data <- data[c(TRUE, FALSE), ]
        keep <- atan2(data$y, data$x) != atan2(data2$y, data2$x)
        createHiveBezier(data[keep, ], data2[keep, ], params)
    },
    required_aes = c('x', 'y', 'group'),
    default_aes = aes(filter = TRUE),
    extra_params = c('na.rm', 'n', 'curvature')
)
#' @rdname geom_edge_hive
#'
#' @export
geom_edge_hive2 <- function(mapping = NULL, data = get_edges('long'),
                            position = "identity", arrow = NULL,
                            curvature = 0.5, n = 100, lineend = "butt",
                            linejoin = "round", linemitre = 1,
                            label_colour = 'black',  label_alpha = 1,
                            label_parse = FALSE, check_overlap = FALSE,
                            angle_calc = 'rot', force_flip = TRUE,
                            label_dodge = NULL, label_push = NULL,
                            show.legend = NA, ...) {
    mapping <- completeEdgeAes(mapping)
    mapping <- aesIntersect(mapping, aes_(x=~x, y=~y, group=~edge.id))
    layer(data = data, mapping = mapping, stat = StatEdgeHive2,
          geom = GeomEdgePath, position = position, show.legend = show.legend,
          inherit.aes = FALSE,
          params = expand_edge_aes(
              list(arrow = arrow, lineend = lineend, linejoin = linejoin,
                   linemitre = linemitre, na.rm = FALSE, n = n,
                   interpolate = TRUE, curvature = curvature,
                   label_colour = label_colour, label_alpha = label_alpha,
                   label_parse = label_parse, check_overlap = check_overlap,
                   angle_calc = angle_calc, force_flip = force_flip,
                   label_dodge = label_dodge, label_push = label_push, ...)
          )
    )
}
#' @rdname ggraph-extensions
#' @format NULL
#' @usage NULL
#' @importFrom ggforce StatBezier0
#' @export
StatEdgeHive0 <- ggproto('StatEdgeHive0', StatBezier0,
    setup_data = function(data, params) {
        StatEdgeHive$setup_data(data, params)
    },
    required_aes = c('x', 'y', 'xend', 'yend'),
    default_aes = aes(filter = TRUE),
    extra_params = c('na.rm', 'curvature')
)
#' @rdname geom_edge_hive
#'
#' @export
geom_edge_hive0 <- function(mapping = NULL, data = get_edges(),
                           position = "identity", arrow = NULL, curvature = 0.5,
                           lineend = "butt", show.legend = NA, ...) {
    mapping <- completeEdgeAes(mapping)
    mapping <- aesIntersect(mapping, aes_(x=~x, y=~y, xend=~xend, yend=~yend))
    layer(data = data, mapping = mapping, stat = StatEdgeHive0,
          geom = GeomEdgeBezier, position = position, show.legend = show.legend,
          inherit.aes = FALSE,
          params = expand_edge_aes(
              list(arrow = arrow, lineend = lineend, na.rm = FALSE,
                        curvature = curvature, ...)
          )
    )
}
createHiveBezier <- function(from, to, params) {
    bezierStart <- seq(1, by=4, length.out = nrow(from))
    from$index <- bezierStart
    to$index <- bezierStart + 3
    data2 <- from
    data3 <- to
    data2$index <- bezierStart + 1
    data3$index <- bezierStart + 2
    fromAxis <- atan2(from$y, from$x)
    fromAxis[fromAxis < 0] <- fromAxis[fromAxis < 0] + 2 * pi
    toAxis <- atan2(to$y, to$x)
    toAxis[toAxis < 0] <- toAxis[toAxis < 0] + 2 * pi
    fromFirst <- ifelse(fromAxis < toAxis,
                        toAxis - fromAxis < pi,
                        toAxis - fromAxis < -pi)
    middleAxis1 <- ifelse(fromFirst, fromAxis, toAxis)
    middleAxis2 <- ifelse(fromFirst, toAxis, fromAxis)
    middleAxis2 <- ifelse(middleAxis2 < middleAxis1, middleAxis2 + 2*pi, middleAxis2)
    meanAxis <- (middleAxis2 - middleAxis1)/2
    middleAxis1 <- middleAxis1 + meanAxis * params$curvature
    middleAxis2 <- middleAxis2 - meanAxis * params$curvature
    nodeR2 <- sqrt(data2$x^2 + data2$y^2)
    nodeR3 <- sqrt(data3$x^2 + data3$y^2)
    data2$x <- nodeR2 * cos(ifelse(fromFirst, middleAxis1, middleAxis2))
    data2$y <- nodeR2 * sin(ifelse(fromFirst, middleAxis1, middleAxis2))
    data3$x <- nodeR3 * cos(ifelse(fromFirst, middleAxis2, middleAxis1))
    data3$y <- nodeR3 * sin(ifelse(fromFirst, middleAxis2, middleAxis1))
    data <- rbind(from, data2, data3, to)
    data[order(data$index), names(data) != 'index']
}