有没有一种方法可以使用 foreach 循环根据一个数据框中的其他数字列将值按行分配给一列？

Question

我有一个包含两列的数据框，一列是数字列，另一列是字符列

我有将近 300 行数字和 url 链接

基于数字列，我想遍历每个 url 从 1 到每行 num 中值的次数

我尝试使用此代码：

sites <- for (i in 1:df$v1) {
foreach (n = i, .combine = cbind) %dopar% {data.frame( paste(df$url, n,sep= ""))}}

但是，此代码仅采用第一个数值并重复所有 url，而不是采用逐行数值

我希望这样:

https://forums.vwvortex.com/showthread.php?9147410-Durango/page1
https://forums.vwvortex.com/showthread.php?9147410-Durango/page2

And so on ...

https://forums.vwvortex.com/showthread.php?9147410-Durango/page14
https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page1
https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page2

And so on ...

https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page5

感谢您对此提供的任何帮助或建议。提前致谢。

Answer 1

如果您想使用 sapply

以一种方式遍历每一行

sapply(1:nrow(df), function(i) paste0(df$url[i], seq_len(df$V1[i])))

#[[1]]
# [1] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page1" 
# [2] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page2" 
# [3] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page3" 
# [4] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page4" 
# [5] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page5" 
# [6] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page6" 
# [7] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page7" 
# [8] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page8" 
# [9] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page9" 
#[10] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page10"
#[11] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page11"
#[12] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page12"
#[13] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page13"
#[14] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page14"

#[[2]]
#[1] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page1"
#[2] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page2"
#[3] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page3"
#[4] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page4"
#[5] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page5"

这为您提供了一个字符向量列表，但如果您只想将所有内容都作为一个向量，则可以 unlist sapply 调用

unlist(sapply(1:nrow(df), function(i) paste0(df$url[i], seq_len(df$V1[i]))))

假设您的初始数据是这样的：

df<- data.frame(url=c(
 "https://forums.vwvortex.com/showthread.php?9147410-Durango/page", 
 "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page"), 
               V1 = c(14, 5))

Answer 2

我们可以用 rep 和 sequence 从 base R

做到这一点

with(df, paste0(rep(url, V1), sequence(V1)))
# [1] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page1"     
# [2] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page2"     
# [3] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page3"     
# [4] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page4"     
# [5] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page5"     
# [6] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page6"     
# [7] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page7"     
# [8] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page8"     
# [9] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page9"     
#[10] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page10"    
#[11] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page11"    
#[12] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page12"    
#[13] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page13"    
#[14] "https://forums.vwvortex.com/showthread.php?9147410-Durango/page14"    
#[15] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page1"
#[16] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page2"
#[17] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page3"
#[18] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page4"
#[19] "https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page5"

或使用 foreach

library(foreach)
out <- foreach(i = seq_len(nrow(df)), .combine = rbind) %dopar% 
           data.frame(Col1 = paste0(df$url[i], seq(df$V1[i])))

数据

df <- structure(list(url = structure(2:1, 
.Label = c("https://forums.vwvortex.com/showthread.php?8943521-Larger-tires/page", 
  "https://forums.vwvortex.com/showthread.php?9147410-Durango/page"
 ), class = "factor"), V1 = c(14, 5)), class = "data.frame", row.names = c(NA, 
-2L))

有没有一种方法可以使用 foreach 循环根据一个数据框中的其他数字列将值按行分配给一列？

Is there a way to use foreach loop to assign values row-wise to a column based on other numeric column within one dataframe?

foreach

for-loop

r

rvest

数据