Question

我想生成一个data.frame的边。当许多边缘在一个节点上结束时，就会出现问题。边缘在向量from和to中定义。

# Data
vertices <- data.frame(id = 1:3, label = c("a", "b", "c"), stringsAsFactors = FALSE)
to <- c("a", "b", "c")
from1 <- c("c", "a", "b")
from2 <- c("c", "a", "a,b,c")

我尝试过的事情：

# Attempt 1
create_edges_1 <- function(from, to) {
  to <- sapply(to, function(x){vertices$id[vertices$label == x]})
  from <- sapply(from, function(x){vertices$id[vertices$label == x]})
  data.frame(from = from, to = to, stringsAsFactors = FALSE)
}

例如create_edges_1(from1, to)，它的输出是：

  from to
c    3  1
a    1  2
b    2  3

例如，from2尝试失败。

所以我尝试了以下操作：

# Attempt 2
create_edges_2 <- function(from, to) {
  to <- sapply(unlist(sapply(strsplit(to, ","), function(x){vertices$id[vertices$label == x]})), function(x){rep(x, sapply(strsplit(from2, ","), length))})
  from <- unlist(sapply(strsplit(from2, ","), function(x){vertices$id[vertices$label == x]}))
  data.frame(from = from, to = to, stringsAsFactors = FALSE)
}

这个想法是要为每个边缘结束的节点“拉伸” to。但是create_edges_2(from1, to)和create_edges_2(from2, to)都抛出错误

rep（x，sapply（strsplit（from2，“，”），length））中的错误：无效的“时间”参数

sapply语句中我在做什么错了？

create_edges_2(from2, to)的预期输出为：

Answer 1

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match

使用f2 <- strsplit(from2, ',') df <- data.frame(from = unlist(f2) , to = rep(to, lengths(f2)) , stringsAsFactors = FALSE)

match

具有联接

library(tidyverse)

map_dfc(df, ~ with(vertices, id[match(.x, label)]))

# # A tibble: 5 x 2
#    from    to
#   <int> <int>
# 1     3     1
# 2     1     2
# 3     1     3
# 4     2     3
# 5     3     3

Answer 2

这是一种方法：

# Attempt 3
library(dplyr)
to <- sapply(to, function(x){vertices$id[vertices$label == x]})
from0 <- sapply(from2, function(x) strsplit(x, ",")) %>% unlist() %>% as.character()
lengths0 <- lapply(sapply(from2, function(x) strsplit(x, ",")), length) %>% unlist()

to0 <- c()
for( i in 1:length(lengths0)) to0 <- c(to0, rep(to[i], lengths0[i]))

from <- sapply(from0, function(x){vertices$id[vertices$label == x]})
edges <- data.frame(from = from, to = to0, stringsAsFactors = FALSE)
edges

根据要求提供此结果：

这个想法是用逗号分隔符分割from，并存储每个元素的大小，以便“拉伸”每个节点。这是通过for循环

完成的

在另一个内部使用rep来根据另一个向量拉伸向量

2 个答案: