如何从边缘列表创建加权邻接表/矩阵? [英] How to create weighted adjacency list/matrix from edge list?

问题描述

我的问题很简单:我需要从边列表创建邻接列表/矩阵.

My problem is very simple: I need to create an adjacency list/matrix from a list of edges.

我将一个边缘列表存储在csv文档中，其中column1 = node1，column2 = node2，我想将其转换为加权邻接列表或加权邻接矩阵.

I have an edge list stored in a csv document with column1 = node1 and column2 = node2 and I would like to convert this to a weighted adjacency list or a weighted adjacency matrix.

更准确地说，这是数据的样子-其中数字只是节点ID:

To be more precise, here's how the data looks like -where the numbers are simply node ids:

node1,node2
551,548
510,512
548,553
505,504
510,512
552,543
512,510
512,510
551,548
548,543
543,547
543,548
548,543
548,542

关于如何实现从此到加权邻接表/矩阵的转换的任何技巧? 这就是我以前决心这样做的方式，但没有成功(由 Dai Shizuka 提供) :

Any tips on how to achieve the conversion from this to a weighted adjacency list/matrix? This is how I resolved to do it previously, without success (courtesy of Dai Shizuka):

dat=read.csv(file.choose(),header=TRUE) # choose an edgelist in .csv file format
el=as.matrix(dat) # coerces the data into a two-column matrix format that igraph likes
el[,1]=as.character(el[,1])
el[,2]=as.character(el[,2])
g=graph.edgelist(el,directed=FALSE) # turns the edgelist into a 'graph object'

谢谢！

推荐答案

此响应仅使用基数R.结果是一个用于表示邻接矩阵的标准矩阵.

This response uses base R only. The result is a standard matrix used to represent the adjacency matrix.

 el  <- cbind(a=1:5, b=5:1) #edgelist (a=origin, b=destination)
 mat <- matrix(0, 5, 5)
 mat[el] <- 1
 mat
 #    [,1] [,2] [,3] [,4] [,5]
 #[1,]    0    0    0    0    1
 #[2,]    0    0    0    1    0
 #[3,]    0    0    1    0    0
 #[4,]    0    1    0    0    0
 #[5,]    1    0    0    0    0

这里mat是从边列表el定义的邻接矩阵，它是向量1:5和5:1的简单cbind.

Here mat is your adjacency matrix defined from edgelist el, which is a simple cbind of the vectors 1:5 and 5:1.

如果边缘列表中包含权重，那么您需要一个略有不同的解决方案.

If your edgelist includes weights, then you need a slightly different solution.

el <- cbind(a=1:5, b=5:1, c=c(3,1,2,1,1)) # edgelist (a=origin, b=destination, c=weight)
mat<-matrix(0, 5, 5)
for(i in 1:NROW(el)) mat[ el[i,1], el[i,2] ] <- el[i,3]  # SEE UPDATE
mat
#     [,1] [,2] [,3] [,4] [,5]
#[1,]    0    0    0    0    3
#[2,]    0    0    0    1    0
#[3,]    0    0    2    0    0
#[4,]    0    1    0    0    0
#[5,]    1    0    0    0    0

更新

一段时间后，我意识到上一个加权边列表示例中的for循环(第3行)是不必要的.您可以将其替换为以下矢量化操作:

Some time later I realized that the for loop (3rd line) in the previous weighted edgelist example is unnecessary. You can replace it with the following vectorized operation:

mat[el[,1:2]] <- el[,3]

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