r igraph - plot() 如何读取布局矩阵？答案

【问题标题】：r igraph - how does plot() read the layout matrix?r igraph - plot() 如何读取布局矩阵？
【发布时间】：2020-09-13 23:36:19
【问题描述】：

我的问题与here 相关，遗憾的是尚未得到回复。我正在尝试自动注释情节上突出显示的社区旁边的文本。中间步骤是了解节点如何放置在图上。

G <- make_graph('zachary')
l <- layout_with_fr(G)
l

布局是一个矩阵，其中行代表节点，列代表 x 和 y 绘图参数。

           [,1]       [,2]
 [1,] 2.8510654 -2.2404898
 [2,] 2.7183497 -1.1815130
 [3,] 3.1429205  0.1117099
 [4,] 1.5585372 -1.0743325
 [5,] 2.2808632 -4.2035479
 [6,] 2.1698198 -5.0526766
 [7,] 1.4938068 -4.6975884
 [8,] 1.9710816 -1.4672218
 [9,] 3.5407035  0.5407852
[10,] 2.2222909  1.9079805
[11,] 3.0784642 -4.5828448
[12,] 4.4115351 -4.1057462
[13,] 0.6002378 -2.2432049
[14,] 2.5010525 -0.1563341
[15,] 4.8914673  4.1417759
[16,] 3.2053338  3.9212694
[17,] 1.1825200 -6.4099021
[18,] 3.7155897 -2.8354432
[19,] 3.8272351  4.2660906
[20,] 3.8636487 -0.5671906
[21,] 2.7302411  3.3998888
[22,] 1.6084374 -2.7407388
[23,] 4.3432855  3.8101278
[24,] 5.9392042  2.2364929
[25,] 6.9980077  0.2389222
[26,] 7.1608499  1.1360134
[27,] 6.0171481  4.0279067
[28,] 5.4996627  1.0367163
[29,] 4.4961257  0.9434659
[30,] 5.5987563  3.2314488
[31,] 2.9958404  1.2022317
[32,] 5.1188900  0.2919268
[33,] 4.1088296  2.5032294
[34,] 4.1686534  2.1339884

但绘图的 x、y 坐标从 -1 变为 1，这与布局矩阵中的最小-最大坐标不同。那么plot(G, layout = l)是如何读取布局矩阵的呢？

【问题讨论】：

标签： r igraph

【解决方案1】：

根据the source，igraph 类对象的绘图方法只是将矩阵从-1 重新缩放为1。

library(igraph)
set.seed(3)
l <- layout_with_fr(G)
        [,1]   [,2]
 [1,] -2.283  0.658
 [2,] -1.289 -0.108
 [3,]  0.146  1.012
 [4,] -1.523  1.601
#... with 30 more rows.
plot(G,layout = l)

maxs <- apply(l, 2, max)
mins <- apply(l, 2, min)
ll <- scale(l, center=(maxs+mins)/2, scale=(maxs-mins)/2)
ll
         [,1]    [,2]
 [1,] -0.2422 -0.1051
 [2,] -0.0704 -0.3821
 [3,]  0.1775  0.0228
 [4,] -0.1108  0.2357
#... with 30 more rows.
plot(G,layout = ll)

请注意，实际的缩放是使用igraph::norm_coords 执行的：

igraph::norm_coords(l)
         [,1]    [,2]
 [1,] -0.2422 -0.1051
 [2,] -0.0704 -0.3821
 [3,]  0.1775  0.0228
 [4,] -0.1108  0.2357
#... with 30 more rows.

【讨论】：