使用 ggraph/ggplot2 在网络图中定位节点和边

Question

我正在尝试使用 ggraph 绘制网络，我想在图形周围添加一个圆圈，边和节点位于圆圈的中心。

使用以下代码（改编自Draw a circle with ggplot2）绘制圆圈效果很好

gg_circle <- function(r, xc, yc, color = "black", fill = NA, lty = NA, size = NA, ...) {
  x <- xc + r*cos(seq(0, pi, length.out = 100))
  ymax <- yc + r*sin(seq(0, pi, length.out = 100))
  ymin <- yc + r*sin(seq(0, -pi, length.out = 100))
  annotate("ribbon", x = x, ymin = ymin, ymax = ymax, 
           color = color, fill = fill, lty = lty, size = size, ...)
}

但我无法将网络层的位置与圆的位置相匹配，这导致节点和边都部分位于圆的外部：

这是代码的关键部分，因为它现在是（使用 ggraph 中的 highschool 作为示例数据集以实现重现性目的）：

library(ggraph)
library(igraph)
graph <- graph_from_data_frame(highschool)

ggraph(graph, layout = "fr") +
  geom_edge_link() +
  geom_node_point() +
  geom_node_text(aes(label = name), 
                 check_overlap = TRUE, repel = TRUE, 
                 nudge_x = 0.1, nudge_y = 0.1) +
  gg_circle(r = 11, xc = 0, yc = 0, lty = 1, size = 0.2) +
  theme(axis.ticks.length = unit(0, "cm"),
        legend.position = "none",
        plot.margin = unit(c(0, 0, 0, 0), "cm"),  
        panel.spacing = unit(c(0, 0, 0, 0), "cm")) +
  coord_fixed()

关于如何解决这个问题有什么想法或建议吗？提前致谢！

Answer 1

我会尝试使用节点位置来找到 r、xc 和 yc 的可接受值。

步骤 1。创建绘图（不带圆圈）：

set.seed(9) # for reproducibility

p <- ggraph(graph, layout = "fr") +
  geom_edge_link() +
  geom_node_point() +
  geom_node_text(aes(label = name),
                 check_overlap = TRUE,
                 repel = TRUE,
                 nudge_x = 0.1,
                 nudge_y = 0.1) +
  theme(axis.ticks.length = unit(0, "cm"),
        legend.position = "none",
        plot.margin = unit(c(0, 0, 0, 0), "cm"),  
        panel.spacing = unit(c(0, 0, 0, 0), "cm")) +
  coord_fixed()

步骤 2。从绘图的 geom_node_point() 层（在本例中为第 2 层）获取数据。修改 gg_circle code 以将此数据框作为输入，并计算适当的圆心坐标/半径：

p.positions <- layer_data(p, i = 2L)

gg_circle_from_position <- function(data, 
                                    color = "black", fill = NA, 
                                    lty = NA, size = NA, ...){

  coord.x <- data[, 'x']
  coord.y <- data[, 'y']

  xc = mean(range(coord.x))
  yc = mean(range(coord.y))
  r = max(sqrt((coord.x - xc)^2 + (coord.y - yc)^2)) * 1.05
  # expand radius by 5% so that no node sits exactly on the line;
  # increase from 1.05 to some larger number if more buffer is desired.

  # no change to this part
  x <- xc + r*cos(seq(0, pi, length.out = 100))
  ymax <- yc + r*sin(seq(0, pi, length.out = 100))
  ymin <- yc + r*sin(seq(0, -pi, length.out = 100))
  annotate("ribbon", x = x, ymin = ymin, ymax = ymax, 
           color = color, fill = fill, lty = lty, size = size, ...)

}

步骤 3。向绘图添加圆圈：

p + gg_circle_from_position(data = p.positions, lty = 1, size = 0.2)

使用 ggraph/ggplot2 在网络图中定位节点和边

Positioning nodes and edges in network graph using ggraph/ggplot2

r

networking

ggplot2

igraph

ggraph